The Study of Plant Life

by Marie Carmichael Stopes

INTRODUCTORY

If you go out into the garden, or fields and woods in summer, and look around you at the plants, you will find that nearly all of them are flowering, or have flower-buds, or have the proof of having had flowers in the shape of fruits and seeds. Even among the few which do not show any of these things, many will probably be plants which you know to be the same as others of their kind which you have seen flowering.

Generally flowers (such as roses and daisies) are easy to see, but in some plants they are less showy, as in the oak, for example, where the little green tails or catkins which come out early in the spring are the flowers. On the whole, however, if you look carefully, you will have no difficulty in seeing proof that nearly all of the conspicuous plants of our gardens and woods bear flowers.

All the same, there are very many other plants, some of them quite easy to see, and others very small and inclined to hide, which do not have flowers at all, and which are so different from the flowering plants that even before you have studied them, you instinctively separate them. The seaweeds or mosses, for example, are at once recognized by any one as being of a different family from roses and lilies.

When you have studied all the plants carefully, you will see how true is this instinctive separation of the chief families, and how nature seems to have made five principal big families, so that both scientists and quite unlearned people see more or less clearly the limits she has set to each.

The family which is most highly advanced is that of the flowering plants, but the others, too, are well worth study, and we will now notice some of the points about their structure which are characteristic of each of the families.

CHAPTER XXIII.
FLOWERING PLANTS

All the plants which have flowers are put into one big family, about which you already know a good deal, because nearly all the plants we have studied up to the present have been plants which have flowers. Let us now go systematically over the chief points about their structure, so that we may have a clear idea of their characters, and be able to compare other families with them.

1. We find that the plant body is clearly marked out into root, stem, leaves, and flowers. The stem may be green and delicate, or it may be thick and strong like an oak tree, and on the stem or its branches we find the leaves.

2. The stem and root have definite strands of “water-pipe” cells, and very often the stems have many rings of wood, one of which is added every year.

3. The leaves are very various in the different plants, but they are generally thin and big, though they are seldom much more compound than those of the sensitive plant.

4. The flowers are easily recognized, as a rule, and consist of a number of parts, some of which are often brilliantly coloured. The stamens and carpels are generally in the same flower.

5. The seeds are always enclosed within the carpels, and have generally two seed-coats.

6. Within the seed are always either two cotyledons, as in the bean, or one cotyledon, as in the grasses. Thus when the seedling grows out of the seed it may have two first leaves or one only.

These are the chief characters of the whole big family of the flowering plants, but this big family is separated into two smaller groups according to the number of cotyledons in the seed. Those that have two form the group of Dicotyledons, those with one the group of Monocotyledons. This may not seem a very important point to form the ground for separating plants with flowers so alike as tulips and roses, but we find that, as well as the number of cotyledons, many other differences distinguish the two groups when we separate them in this way. For example, the Dicotyledons have the veins of their leaves so arranged as to form a network, as in the lime, while the Monocotyledons have them parallel, as we noticed in the grasses and lilies.

We also find that it is only in the Dicotyledons that the plants have rings of wood in their stems, as is the case in the lime, oak, and many others.

In the numbers of the parts of the flower, we also find differences between the two groups; for example, the Dicotyledons have generally two, four or five, or a multiple of these numbers such as ten, as we see in the poppy, primrose, rose, and many others; while the Monocotyledons have the parts of their flowers in three or multiples of three, as in the lily, tulip, and daffodil.

These differences between the Monocotyledons and Dicotyledons, however, are not nearly so important as their likenesses, for they agree in the main points (1) to (6), and therefore belong equally to the great family of the flowering plants, which is the most important family now living.

CHAPTER XXIV.
THE PINE-TREE FAMILY

Since trees such as the oak, beech, and lime all belong to the family of flowering plants, you may be surprised to find that the pine-trees are separated from them. Yet all the trees like pines, Christmas trees, larches, and many others, form a family of their own. You will see why this is, if you look at a pine-tree carefully, and compare its characters with those we saw in the flowering family. In the first points the two families are alike.

1. We find that the pine-tree body is clearly marked out into root, stem, leaves, and cones.

2. Also that the stem and root have definite strands of “water-pipe” cells, and that the stem has rings of wood, one of which is added every year.

3. The leaves vary a little in the different members of the family, but the commonest kind of leaf is the fine sharp “needle” leaf of the ordinary pine (see fig. 53). In almost all cases the leaves remain on the tree for more than a year; they are evergreens (it is only the larch among the English-growing members of the pine-tree family which has new leaves every year), and the leaves are simple and strong, and well protected.

4. There are no “flowers,” but the two kinds of cones which take their place are easily recognised. The two kinds of cone generally grow on different branches of the tree, the small ones only live a short time and scatter the pollen, and the larger ones often remain two or three years on the tree, and form the seeds. The wind scatters the pollen; you will remember in the spring-time before the leaves are out, how the “sulphur rain” showers down from the pine-trees; this is the yellow pollen, which is blown in clouds on to the seed-bearing cones. There are millions of pollen grains scattered in this way, and but few of them ever reach a cone. You will remember that many of the flowering plants could afford to make small quantities of pollen, as they had special carriers in the insects to take it from flower to flower.

Fig. 123. A branch of Pine with a small young seed-bearing cone, and a large ripening one.

Besides the pollen cones, you should find two sizes of seed-cones on the tree: some quite small, and green or pink, and some large ones which are brown and ripe. It will be easier to see their structure at first in the big ones; they consist of a number of brown scales packed neatly one over another. If you pull these apart you will see that each of them bears two seeds on its upper side.

Fig. 124. Larch. A and B, young scales, showing (i) inner seed-bearing scale, and (o) outer protective one. A, side view; B, front view; C and D, old scales, C from the side, D from the front, showing how the inner scale increases more rapidly than the outer.

5. The seeds are always seen to be lying quite openly on the upper side of the scales, and are not covered in by closed carpels as they are in the flowering plants. Each of the scales (which bears its two seeds) corresponds in a way to the carpel in a flower, but there is an important difference in the fact that it leaves the seeds open. In old pine cones there seems to be only one scale to each pair of seeds, but there is really a second smaller one outside it—which is sometimes quite difficult to see. It shows better in the larch, where the outside one is much the bigger of the two in the young cones, and gradually gets left behind, as the inner scale grows very fast (see fig. 124). Notice, too, how the ripe seeds have one-sided wings, which split off from the inner scale, as you can see if the cone is not too ripe. This wing is on the seed itself, not on a fruit, as is often the case among the flowering plants. The wing helps the seed to fly, and in the late autumn (in many cases two years after it began to grow, for some pines grow very slowly) it is scattered with its brothers. If you are ever near pine trees when there has been snow, you may see it sprinkled with these winged brown seeds.

Fig. 125. Winged seed of the Pine.

6. You may never have seen a baby pine tree. If not, you must get some seeds and grow them. They grow very slowly at first, and may take six weeks to show above ground even in summer; but they are well worth waiting for. Notice how they come up (see fig. 126), and that at the beginning of their growth, as they come out from the seed, they have seven or even as many as twelve first leaves, and these leaves are really the cotyledons, as you may see by cutting a seed across. So that instead of the one or two cotyledons of the flowering family, we find in the pine family that there are many cotyledons, and that their number may vary from five to ten or more.

Fig. 126. Stages in the growth of Pine seedlings; (c) cotyledons.

If you go back over these points, you will see that we have found a large number of differences between the flowering plants and the pines. Of these, the most important are the points (5) and (6), which alone would be enough to make us place the pines and flowering plants in separate families, though point (4) is also very important. We find, however, that the pines are more like the flowering plants than are any of the other families, so that they are the nearest relatives the flowering plants have, even though they are rather far-away ones.

PLATE III.

TREE FERNS, SHOWING THEIR TALL THICK TRUNKS AND LARGE LEAVES, WITH SMALLER FERNS GROWING BENEATH THEM

CHAPTER XXV.
FERNS AND THEIR RELATIVES

Perhaps there is no family of plants so easy to recognise as the ferns. It is nearly always a simple matter to know whether or not a plant is a fern, for although there are hundreds of different kinds, they all have the family characters plainly marked.

We have not very many ferns growing commonly in England, for they generally require a moister air than is usual in this country. By far the commonest is the bracken, which grows in all parts of the country, and sometimes in very large masses (see Plate I.). Some people separate the bracken fern from the others, and speak of “bracken” and “true ferns,” but this is not at all correct, for the bracken is just as much a true fern as the others, only as it is so much commoner, people are apt to value it less.

In some countries, particularly in the tropics, there are (as well as ferns like ours) very large ferns with tall, strong, upright stems, and crowns of large spreading leaves. Such ferns you can see in Plate III., and they are called tree ferns. Notice how thick the stem is, and how large the leaves are compared with it, while the trunk seems to be all rough and hairy, which is due to the jagged bases of the old leaves which have fallen away. Yet even the tree ferns are easily recognised as belonging to the fern family.

Let us examine ferns in order to find out what are the points about them which are specially characteristic for their family, and which help us to separate them from the other plants.

1. We find that the fern body is clearly marked out into roots, stem, and leaves, but there appear to be neither flowers nor cones.

2. The stem and roots have definite “water-pipe” cells, as you can see if you examine a thin slice with your magnifying-glass, but there are never rings of wood formed year by year, as in the higher families. The stems are frequently short and stumpy, and often run underground. They are usually covered by the rough leaf-bases of old leaves and by dry scales.

3. The leaves are generally few in number, often only three or four, but they are highly compound, and are split up into very many side leaflets. They are generally thin and delicate. When they are young they are rolled up in the bud in a close coil (see fig. 127), and as they unfold they bend back. This way of coiling up is quite a special character of ferns. The buds are generally covered with flaky, shining scales, which stick all over the young leaf-stalk.

Fig. 127. Young leaf of a Fern rolled in a close coil.

4. You have never seen a fern with flowers or seeds, yet there are always plenty of new ferns every year. How are the young ones formed? For a long time botanists did not know, so that people thought there was some magic about it, but now we know the whole story, and it is a very interesting one.

5. There are no seeds, and

6. Therefore there are no seedlings to have cotyledons.

You must have noticed little dark brown spots on the backs of some fern-leaves. It is in them that you must look for the beginning of the new fern plants. The little patches are at first hidden by green coverings, but when they are ripe these bend back, and expose the little brown clusters within. If you look at one of these ripe patches with a magnifying-glass, you may be able to see a number of little roundish boxes on stalks. Each of these contains a number of tiny “spores” (which are single cells with the power to grow), and when the spore-cases are ripe they open and shoot out the spores, as you may perhaps see if you look closely at a ripe patch when it is taken into warm, dry air.

Fig. 128. A small piece of Fern leaf showing the patches of spore-cases on the under side.

These brown patches are not at all like flowers, but in some way they do the work of flowers, for they give rise to cells which can carry on the life of the fern to a second generation. The way in which they do it, however, is totally different from that of the seed, and is quite the most special character of the ferns and their relatives.

The spores grow slowly when they come on to moist earth, but as their development takes a long time, you had better get some from a gardener which have already grown. As the spore grows, the one cell composing it divides and divides again, until there is formed a little filmy heart-shaped green structure called a prothallium (see fig. 129), which is not in the least like a fern plant, for it is not more than a quarter of an inch across. It has no stem or leaves, and is only a thin layer of green cells, with a few root-hairs on the under side. Two of the cells formed on this little structure then unite and begin to grow while still attached to it, and finally they grow into the form of a very small, simple fern plant (see fig. 129). So that between the old fern plant and the little fern “sporeling” (for we cannot call it a seedling) we find a whole new structure, the prothallium, which is quite different from the usual fern plant. This curious alternation of fern,—prothallium,—fern, and then again prothallium, is what we call “alternation of generations,” and is very characteristic indeed of the fern tribe.

Fig. 129. A Prothallium (p), with a young Fern (f) growing out from it. (Magnified).

Some ferns take a short cut, and bear little ones directly on their leaves without any prothallium. You see this in the “Hundreds and Thousands” fern, where the old plant is sometimes covered over with little ones, which will grow if they are taken off and planted carefully.

Sometimes people are deceived by what is called the “flowering fern,” and expect that it will have flowers. In this fern we find that all the spore-cases grow together on a special leaf, which is so covered by them that it looks quite different from a usual one, and is called the flower, though it is not one. In all other ways the story of the spore building and growth is like that of usual ferns.

In our study of ferns, you see that they have many characters which are exceedingly different from either the flowering plants or pine-trees. In fact, they are so different that we require to add some new points to our list of characters for family divisions, which are:—

7. Instead of flowers there are little spore-cases, which contain a number of simple one-celled spores. These are generally found on leaves which are otherwise like the rest of the leaves of the plant.

8. Each spore grows out to form a small green structure, which differs from the parent, and which we call the prothallium.

9. The new fern-plant grows at first attached to the prothallium, but soon grows out beyond it, and is quite independent.

What we call “ferns” are not the only plants which belong to this big family, for the club-mosses and also the horsetails have almost the same arrangement for their building of new plants. Our character-points (7) (8) and (9) apply to them, even though the rest of their structures appear to be so different from the ferns. They are, therefore, put in the same big family with the ferns, though they have smaller classes for themselves apart from the true ferns.

Neither the ferns nor their near relatives are very important in the vegetation of to-day, but very long ago they were among the chief plants in the world, and grew to be as big as forest trees. Even then, however, they had almost the same way of forming spores that they have to-day, a fact which still marks them out as a family different from all the other families of plants.

CHAPTER XXVI.
MOSSES AND THEIR RELATIVES

Mosses form another big family, the members of which are generally easy to recognise, even when you know little about them, because they all have a very strong family likeness. If you look for mosses in a shady wood, or on stones and tree stumps near a waterfall, you will often find large numbers of them growing together, sometimes forming sheets of soft green, covering the stones and earth and tree stumps. These luxuriant mosses grow, as a rule, in moist and shady places, but there are others which grow on dry walls or between the cobbles of little-used paths, and generally form brilliant green patches of tiny plants, like masses of velvet. If you pick out a separate plant from among these and look at it through a magnifying-glass, you will see that it is very like the bigger ones of the wood.

Fig. 130. A clump of Mosses, showing the flower-like appearance of the tips of their branches.

For our study it is perhaps better to choose one of the bigger ones, because all its parts show so clearly.

1. If you take a single plant, you will find that it appears to be marked out into root, stem, and leaves, though all these parts are small and simple.

2. The stem is delicate, and you will not be able to see any “water-pipe” cells when you examine it with your magnifying-glass.

3. The leaves are always very simple and small, generally narrow, pointed, and clustered thickly round the stem with no special leaf stalks.

4. At the ends of the stems, you will often find little structures, sometimes rather pink in colour, which look something like flowers (see fig. 130), but they are really quite different in their nature from true flowers.

Fig. 131. (a) The part of the Moss corresponding to the prothallium; (b) with the spore-capsule attached; (c) enlarged capsule, showing the covering; (d) naked capsule, showing the lid which falls off at (l).

5 and 6. There are no seeds and no seedlings.

7. At the top of some of those plants which seem to have flowers you will find later that a long slender stalk grows out with a little capsule or box at the end of it (see fig. 131 (b)). This single box or capsule really corresponds to the numbers of small spore-cases on the backs of fern-leaves, for it is in this capsule that we find the spores, which are simple and single-celled like those of the fern.

8. When these spores grow, however, they do not form a prothallium as they do in the ferns, but they grow out into the leafy moss-plant.

It is very difficult really to see how this can be the case, unless you study mosses very carefully with a microscope, but all the same it is true that the leafy moss-plant corresponds to the prothallium of the fern.

9. On the leafy moss-plant you find the simple stalk and capsule which gives rise to the spores; this spore forming part of the plant always remains attached to the leafy plant, so that we find the two portions of the plant in contact all their lives, and not separated as they are in the fern.

Fig. 132. A piece of Liverwort, showing the flat, creeping body, not divided into root, stem, and leaves.

The only other plants which are built on anything like this plan are the liverworts, though you might hardly believe it, because most of them are not marked out into leaf and stem at all, but are only flat, creeping, green structures, which do not look in the least like the mosses. It is true that they are not very near relatives, but because they have spore-cases rather like those of the mosses in some very important ways, the scientists have put them together in the big moss family. The true mosses have a special smaller family to themselves within this, a family which is quite easy for you to recognise when you go out on your rambles into the woods.

CHAPTER XXVII.
ALGÆ AND FUNGI

The last big family of plants is that containing the simplest plants of all. They are often very small and apparently unimportant, sometimes so small that we cannot study them at all without magnifying them very much with the microscope. In other cases they are quite large and easy to see; for example, the big red and brown seaweeds, and the many toadstools in the autumn woods. Sometimes they may even be very huge indeed, as are some of the seaweeds which grow in tropical seas. All the same, though we examine one which is as big as can be, it is really more simple in its detail than the mosses.

In very many of the algæ and fungi, the whole plant body consists only of one single cell. When this is the case, the plant lives floating or swimming about in water, or in very damp places. In rain-water which has stood for a long time you may find numbers of these tiny algæ. If you put some of the water in a glass tube and hold it against the light you may just see them, with a magnifying-glass, as specks of green, often swimming actively about.

The fine green “scum” which floats on many ponds and slow-moving streams consists of masses of these simple plants, in this case generally of forms in which the single cells keep attached together in long rows or chains, forming hair-like plants. Colourless plants of this kind are the fungi, which are often built on the same plan as the hair-like green algæ, only they do no food-building work for themselves, but live as parasites on other things. This is the case in many moulds and the plants which form potato-disease, and, in fact, the greatest number of plant-diseases are caused by such simple parasites.

All these plants are very small and simple, and as you can see at once, are not at all to be compared even with the mosses, but there are others which seem to be more complicated, as are the big seaweeds and the toadstools. Let us see how it is they are put in the same family as the simplest plants of all.

You can see, even with your magnifying-glass, that they have no special “water-pipes” in what you may call their “stem,” (for want of a better name), but that their whole body is built up of numbers of soft cells all very much alike, which twine in and out, and build a kind of soft weft; they have no really marked out stem and leaves. Look at a toadstool, for example, there is just a stalk and a cap spreading out above ground, while under the ground there are many twining thread-like strands (see fig. 133).

Fig. 133. A Toadstool, showing the “cap” and “stalk.” Under the cap are the radiating gills, on which the spores are formed. Thread-like strands under the soil.

Even in the seaweeds, which may seem to have stems, you will find that such is not really the case. They have generally a flat body, which is thin at the edges, with a stronger mid-rib, and the flat edges get worn away in the older parts of the plant, and so leave the mid-rib looking like a stem, though it is not so really (see fig. 134).

Fig. 134. A Seaweed, showing the branched body, which is not divided into stem and leaves.

When we come to look for flowers or even spore capsules, we see still more clearly how simple these plants are; they have not nearly such a complicated history as the moss. For example, in the toadstools we find that there are many spores formed directly on its lower surface, on the “gills,” and these grow out to form new toadstool plants. You can see the spores if you cut off a toadstool or mushroom head which looks full grown and is quite expanded, and then lay it on a sheet of gummed paper over-night, with the gills downwards, and another beside it with the gills up. Next day you will find that the paper under the one where the gills were downwards is covered with radiating lines of spores, just as they fell from the gills, and repeating their pattern.

Fig. 135. Part of a Bladder-wrack, showing the floats (f) and special swollen tips (s).

The seaweeds have the most complicated way of forming spores of any of this family. There are special little swellings at the ends of the plant, as in the ordinary bladder-wrack, for example (fig. 135 (s)), and in these are formed the cells which will give rise to new plants. The other simple bladders (fig. 135 (f)) are only full of air, and act as floats to keep the plant up in the water.

In this the simplest family of all, we find more variety in the appearance of its members than in any of the others, so that it may seem to be rather difficult to recognise the plants which belong to it. Perhaps the easiest way of settling this, is to see if the plant fits into any of the other families, and if it never has flowers nor cones, neither fern spore-capsules nor the big spore-capsules of the moss family, then you are fairly safe in classing it with the simplest plants.

Very many of the plants of this family are found living in water, which is perhaps one of the reasons that they can afford to be so simple, because the water protects them from many of the dangers land-plants have to prepare against, such as wind, drought, or too much sunshine. This is the simplest family of real, undoubted plants; but there is one class still simpler, and that is the family of bacteria, about which you must have heard much, as many of them cause our diseases, though others do much valuable work for us. All the same, we will leave these little creatures alone, and content ourselves with the five great families of plants which we can see with our own eyes.

PLATE IV.

A LOW EDGE OVERGROWN WITH FOXGLOVES AND MANY OTHER WILD PLANTS

PART V.
PLANTS IN THEIR HOMES

CHAPTER XXVIII.
HEDGES AND DITCHES

We do not see plants growing under quite natural conditions in the hedges and ditches, because they are put there by man in the first instance, and are continually kept in order by him. All the same, the hedgerows, which are so common in England, deserve a little study. They are within the reach of every one, and there we may often find many wild plants growing sheltered by the actual hedge.

The principal plant is, naturally, the one which forms the hedge, and this is very commonly the hawthorn; but, growing under it, and over it, and on the banks on either side, there are many others which are generally quite self-planted and truly wild. Of the bigger ones, the white clematis or Travellers’ Joy is very common in the south of England, and grows climbing all over the hedge, and often covering it with its white flowers. We noticed this plant among those which are special climbers (p. [105]), and we can often see very well on the hedges how it climbs over tree and shrub, and supports itself on them.

A smaller plant, of somewhat similar habit, is the goosefoot. This has long, weak stems, which grow up amidst the other vegetation and so support themselves, while its leaves are arranged in whorls round the stem, and are narrow and rough, and help to keep the plant from slipping down. Notice also its fruits, how rough they are, and how they cling to everything. They are beautifully adapted to catch on to every passer-by, whether man or animal, and so to get carried to a distance where the seeds may grow.

A character of the ordinary plants growing in the hedges is the tendency they often have to form very long, straggly stems, which are too fine and weak to support themselves, but which are quite strong enough to grow up through the hedge and bear leaves, as they are partly held up by the other vegetation. You may frequently find plants which are usually only a foot or so high, and able to support themselves very well, growing up through the hedge to a height of two or three feet, and having thin, limp stems with long spaces between the leaves (see fig. 136). These plants have some of the characters both of those grown in the dark and of climbing plants, because the thick-set hedge keeps off the light from the low-growing parts, so making them straggly, and at the same time gives them the support they need if they grow rapidly out into the light, and do not build strong stems. Very often you may find plants of the same species as those that grow so tall in the hedge, growing in the shorter turf away from it, and there only reaching their usual height.

Fig. 136. Two Toadflax plants growing near together: A, on the bank by a hedge; B, among the plants of the actual hedge.

This shows us not only that different species are specialised to grow under different conditions, but that even two individual plants of the same species may be growing within a few feet of each other, and yet have quite a different appearance owing to the influence of their immediate surroundings. There are many such cases to be seen in the hedgerows.

If the hedge runs from east to west, it will cast a shadow over the side lying to the north. Notice how different is the general appearance of the plants on the bleak side from that of those on the south. You may also find that some species which grow on the south side do not grow on the north at all, or only in far smaller numbers. It is quite worth while making out lists of all the plants you can find on one side and the other of the hedge if it is a big, well-established one, and comparing the numbers and condition of the two sets of plants.

Fig. 137. A, Dead Nettle which has grown up through the hedge. B, the same after being cut back with all the others. Side branches have begun to sprout now that it is well lighted and the top has been cut off.

As we noticed before, hedges are not entirely natural, and as man therefore forms a part of the plants’ environment, it is quite interesting to see how they respond to his influence. For example, we may study the effect of his trimming the hedge. In a hedge which had been left for some time to itself, the plants would have long, thin stems, bare at the base, where no leaves would develop, as they would be cut off from the light by all the other plants. Then comes the “hedger and ditcher,” and cuts them all back, leaving often only a few inches of nearly leafless stem. What is the result? Soon on these bare stumps leaves begin to sprout now that the light can get at them and the top is cut off, and many short side-branches come out, also bearing leaves, so that where before were only long, bare stems carrying the top tufts of leaves out to the light, we now have short, thickly clustered plants of bushy appearance (see fig. 137). Soon, however, the race for light begins again, and the plants grow taller in their attempt to overtop each other. Notice also how the hawthorn (or whatever woody plant it may be which makes the hedge) responds when its leafy shoots are cut away. Many hidden and sleeping buds in the brown woody stem now get their chance and wake to active life. It is this continual cutting back which makes the hedge so thick with many short branches.

Fig. 138. Bulrushes growing in a wet ditch.

In the ditches, which often run alongside of hedges, we find quite a different set of plants. The ditches are generally cut out to a lower level than the surrounding bank, and so they often contain water while the rest is dry. In such watery ditches the plants which you will find depend a good deal on the quantity of water in the ditch, and whether it is always there or not. If it is really a wet ditch, you may get many of the inhabitants of the lakes, or if it is a dry ditch where but little moisture collects, you will get only rushes and rank grass. An interesting kind of ditch to watch is one which is well supplied with water nearly all the year round, but may dry up during the height of summer. In such a position as this you are nearly sure to find many pond-dwellers, such as water-cress, duckweed, water parsnip, water buttercups, bulrushes, reeds, and many others, which will vary with the locality. These plants generally choose a spot where there is a permanent supply of water, but plants cannot foresee the unexpected draining of the ditch, or a summer drought, and they are sometimes left through these causes to grow on bare mud. When this happens, notice how they behave; those which were already rooted in the mud may continue to flourish for some time, while those which were floating may be able to root themselves and tide over a short danger. If the water is permanently drained off, however, they gradually have to give in; they seem to draw themselves together and the long, luxuriant branches die off, only the short shoots remaining, which are not so extravagant with water. The duckweeds, which you know very well as little floating green leaves, have long, thread-like roots hanging from them unattached to the soil. When the water goes, they first root themselves in the soil with these water-roots, but if the drought lasts long the roots die away and the plant hides in the mud, where it can remain for a long time waiting for the return of the water.

Fig. 139. Duckweed, with simple leaves and long roots hanging in the water.

In the ditches you will probably find a number of green, thread-like algæ; these may also remain on the mud for some time when they are dried up, and in their case some of the cells at such times get a specially thick coat, and remain living for long. Then, if the water returns, it is again the home of these algæ, which rapidly grow out from their protected cells.

So that you see, even if you had no plants but those in the hedges and ditches to study in their homes, yet you could manage to find many examples of living plants which are trying to fit themselves to their ever-changing surroundings. Those that cannot succeed must die away in that spot, and confine themselves to some other place where the struggle is not too hard for them. All the plants which we find anywhere living together are, therefore, those which are suited to the conditions in that place, and all such plants growing together in this way form what is called a “plant association.”

CHAPTER XXIX.
MOORLAND

Fig. 140. A moorland stream. Notice the low growth of all the plants.

The word “moorland” brings at once to the mind’s eye great stretches of land which the farmer has left practically untouched. It is not like a woodland, for the plants are all so short that they do not shut out the view; hence on the moors there is a sense of space, and one can see all around the hillsides and plateaux clothed, though their form is not hidden, by their covering of plants. Let us see what are the characters of the plants which grow so lowly, and yet so thickly on these expanses of uncultivated ground. Almost the first which rises to one’s mind is the heather, with its short, bent stem and many wiry branches. If you try to pull it up you will find that the roots are long and fine, but strong, and that they grow for great distances into the soil, so that it is very difficult to get the plant out. The leaves are small and tough, and the lower ones on the stems generally have their edges half rolled in, while the leaves on the ends of the branches which stand further out in the air are often so much rolled as to be almost entirely closed. Some of the heather-plants seem to be covered over with short hairs like soft down, while others have shiny strong leaves. In fact, the heather has many of the characters of plants which have to protect themselves from drought.

Look at the others growing with the heather; there is the heath, which is so like it that almost the same description applies to it. Then there is the cranberry, which lies close to the ground, and is somewhat protected by the other plants, and has more delicate stems, and larger, flatter leaves, which are also rolled in at the edges. The bilberry has certainly larger leaves than these others, but notice in the early autumn how soon and readily they drop off, and leave the thick, green, ridged stem to do their work. The moorland grasses also have protected leaves; generally they are narrow and pointed, and the whole leaf rolls over, so protecting the side on which are the transpiring pores (see p. [102]). All these plants have the appearance of protecting themselves from loss of water; how is it? It may seem strange when you remember that it is from our moorlands that so much of our water supply comes, and also that the moors are common in the north, where there is a large rainfall. All the same, the plants on a moor do actually require to preserve their water, as they suffer from “drought conditions.”

Stand on a high moor on a windy day, and you will soon feel how the force of the wind sweeps across it. Such a day is what laundresses call “fine drying weather,” and so do the plants. Then if you go on a bright sunny day in summer, you will soon feel how very hot the moorland can be, for there is no shade to be had anywhere, and the cool green glades of a wood offer a tempting change. The moorland plants suffer from this heat, and require to protect their transpiring pores from the glare, so that you will find all those that can do so, have rolled their leaves up tightly. Then notice the soil of the moors, how springy it is, and how black and “rich”; very often there are traces in it of the partly decomposed plants which form it. This is what is called a peaty soil, and may even be true peat. The decomposing plants in this soil give rise to an acid which is rather preservative, and at the same time it acts on the living plants and makes it difficult for them to draw in water by their root hairs. This kind of soil adds very greatly to the “drought conditions” of the moorland plants, for it makes it hard for them to use the water which surrounds them. All these things cause the moorland plants to be as sparing as possible of their water, and so they have the appearance of plants grown under dry conditions.

But why are there no trees on the moors, you may ask! It cannot be that they are on too high a level for trees to grow, for some even higher hills are clothed with them. The truth is that probably long ago there were trees on the moors, but men cut them down foolishly without having planted young ones between the old ones, which would have replaced them. When once all the trees are cut down on a hillside, it is very difficult for young ones to get a start again, because everything which makes it hard for ordinary small plants to grow hinders the young trees, and the worst of all these things is the strong wind, which can rush unchecked over the bare moor. A strong wind is more powerful than a young tree, and kills it.

The plantations of young trees which are to be found on the moorland have to be started on the sheltered side, and require much care and attention. You will notice that the trees which do grow there are those which are specially fitted for a hard life, such as the pine, larch, and birch.

Another feature of the moorland, and one which cannot long escape our notice if we walk about moors at all, is the number of patches of wet moss which shake and tremble beneath our feet, and may form great stretches of bog-land. Sometimes this is so soft that it gives way altogether, and one may be knee-deep in moss and water, where it looked firm enough to the eye. You will find this bog moss grows in a peculiar way, the fresh green branches growing up and up, while below lie the half dead older stems, which are partly preserved by the peaty acids. These layers of moss collect for many years, till very thick masses of peat-bog may be formed.

Among the bog-moss you will often find the sundew and butterwort (see pp. [114]-[15]), which are two of our chief insect-eating plants. They love the boggy moorland, or a damp spot beside a little moorland stream.

There is a curious thing you may have the chance of seeing in a wet moor. If you find a stream dripping over a ledge some little distance on to the rocks below, you may see how thick and beautifully green are the patches of moss growing beneath its spray. If the stream has passed over much limestone (and is therefore carrying some in solution), you may see below the living moss much dead moss just covered with a thin coating of lime. Below this is more moss, which has been made quite hard with the lime, and is brittle and snaps if you try to bend it, while below this again is a hard, compact mass of stone which is made from the stony stems of the moss crushed together by the weight above them and filled in with more deposited lime. In some places great masses of rock are formed in this way. You have here, acted before your eyes, a piece of the history not only of the living and dying plants of to-day, but of the building of rocks, which may some day help in the building of mountains.

PLATE V.

WATER PLANTS GROWING PARTLY BELOW AND PARTLY ABOVE THE SURFACE OF THE WATER

CHAPTER XXX.
PONDS

The water of a natural pond is crowded with plant-life. Do not go to one in a London park, which is cleaned out by the County Council at intervals, but to one which is left to itself, and you will find it full of interest.

Fig. 141. Water Buttercup, showing the much-divided water-leaves, and the simpler leaves rising into the air.

Some of the plants float freely in the water, as do the duckweeds, and others, such as the water-lilies, are rooted in the mud with their leaves floating on the surface, while yet others are rooted in the mud at the bottom and live almost entirely under water, like some of the potamogetons, or curly pond-weeds. The plants which are more or less attached to the muddy bottom, and have floating as well as submerged leaves, are perhaps among the most interesting, for they show two kinds of leaves. Look at a water buttercup, for example (fig. 141); on the surface of the water, or just above it, are the flowers and leaves, which are rather like the leaves of an ordinary buttercup. Follow the stem a little way down under the water, and you will see that the leaves are no longer simple, but are split up into many hair-like divisions, which sway about easily with the water’s movements. These two kinds of leaves are each suited to their position, as you will see if you think about them. The broad, undivided leaves on the top of the water expose their surface to the sunlight and do as much manufacturing of starch as possible, while the soft much-divided leaves below the surface are in keeping with their position, for they allow the current to pass between their fine divisions instead of pushing them up or tearing them, as it must do if they had broad, flat surfaces, which would be overpowered by the strength of the current.

Compare these leaves with those of the water-lily. In the lily you find no divided leaves, but they all rise to the surface and float there, spreading their expanded blades on the water. Notice what very long leaf-stalks they have, sometimes eight or ten feet in length. Think how absurd the plant would look on dry land, with its short stem and its huge leaf-stalks, though they are so well suited for floating in the deep water. In the air the long, soft stalks would flop about on the ground, as they need some support, but this they get in the water, which buoys them up and saves them from expending too much material in the formation of strengthening tissue.

Even those plants which, like the water marestail, can stand up by themselves some way out of the water, yet have softer stems than most land-plants, and far fewer well-developed “water-pipe” cells, because they are so surrounded by water that they can get it easily. Both these plants and the water-lilies, as well as many others, store air rather than water in their stems, and often the spaces in the meshes of the stem-tissue are filled with air, which acts both as an air reservoir and a buoy to float the leaves. We find all through the plant-world that the structure of a plant depends very much on the kind of conditions under which it is living, and in the case of those growing in the water, it is quite clear how the soft, air-filled stems are one result of their mode of life, and are well adapted to it.

Fig. 142. Duckweed, with simple leaves, and long roots hanging in the water.

In the ponds you will often find that the duckweed grows in large masses on the surface. Each plant seems to consist of but one leaf and a slender root about an inch long, hanging freely in the water. Sometimes two or more of the leaves are attached and form a little cluster, but it is exceedingly rare to find the duckweed in flower. Simple as it is, almost suggesting the algæ rather than the flowering plants by its general appearance, yet the duckweed is really a flowering plant. It is, in fact, one of the very tiniest of flowering plants which are known.

Floating with the duckweed are frequently many fine, thread-like algæ, sometimes quite free, and sometimes attached to stems or rocks. They are very delicate, unprotected plants, their whole body consisting of simple rows of cells. Notice how their feathery tufts cling together in a close mass when they are taken out of the water; they require its support and protection to enable them to live.

Fig. 143. Creeping rhizome of the Bulrush, which pushes out towards the middle of the pond.

There are many plants growing round the borders of the pond, half in and half out of the water, such as the reeds and sedges, irises and the tall marsh buttercups. Watch how these plants gradually grow further and further in towards the middle of the pond. They advance with their creeping underground stems (see fig. 143), and collect mud, dead leaves, and stalks around them, gradually building up a little firm soil round their roots. Slowly these accumulations from different plants meet, and the whole gets more compact, till the plants from the shore which require soil are able to grow with them.

Fig. 144. A water channel grown over by floating plants and the advancing reeds and rushes.

In this way the shore slowly advances, the floating plants first building up some mud, and the reeds following and bringing shore plants in their train, till in the end the edges of the pond all meet in the middle, and the pond, as such, no longer exists. Only a marsh remains, till this may be gradually grown over by the ever-increasing land-plants, and an oak-tree may grow where once the water-lilies bloomed. If the advancing reeds at the edge had been kept cut back, as they often are, then the land-plants could not have taken such hold, and the pond would have remained a pond with all its “water-weeds.”

PLATE VI.

LOOKING DOWN ON A SANDY SHORE AND RIVER MOUTH

The long spit of sand-dune A protects the marshy land B from the strength of the waves, and here many salt-marsh plants grow. C is the open sea, which at full tide beats on the sandy shore so that no seaweeds or marsh-plants can grow on this side of the dune.

CHAPTER XXXI.
ALONG THE SHORE

Sandy shores with dunes are so common round Britain that you will probably have opportunities of studying them. Did you ever notice with any care what kind of plants grow on the sand next the sea? As you walk inland from the sea, you will find first little hummocks of sand with a few low, bent grasses, scattered and often far apart. Then as you go a little further inland, the sand mounds are higher, and a stronger grass grows first in tufts and then thickly over them; this grass is the useful sand-binder, or marram grass, and grows on the shifting sand, quite near the sea (see fig. 145). Try to pull up a plant of this grass, and you will probably find out some of the things which help it to hold its position in the moving sand. It is not at all easy to pull up, and you will have to dig rather carefully if you are to get it out at all complete.

You will find that what you thought was a simple tuft of grass is really connected, by an underground stem, with other tufts. If you follow this along, you will find that the underground stem runs for a long distance, burrowing in the sand and sending up tufts of leaves at intervals. The tip of the stem always remains under the sand, prepared to grow in whatever direction is best, and unless it is buried to a very great depth it will always continue growing. Coming off from the stem there are very many long roots, and at the places where the leaf tufts arise there are generally one or two much longer and stronger than the others, which run a very great distance into the sand, and if you wish to get them out without breaking them, you may have to dig for several hours. It is by means of these branching underground stems and long roots that the marram grass gets its hold on the sand. When once this grass holds the sand it is soon helped by a number of other plants, which come on behind it and cover the surface, and so prevent the wind from scattering the sand-grains, and blowing them about in clouds.

Fig. 145. A Sand-dune by the sea with the Marram grass in tufts, and the Carex tufts coming up in straight lines from their underground stems.

One of the first plants to follow the marram is the sea-star grass, or carex. You have probably seen its little tufts following in lines across bare banks of sand (see fig. 145). This appearance is due to the underground stem, which runs very great distances in nearly straight lines, sending up groups of leaves at short intervals as well as side-stems, which form lines crossing the main line. Often a bank may be covered with lines of this plant. A little piece of the plant is shown in fig. 146, where you can see that the structures are on very much the same plan as those described for the marram grass. There are many other plants with this kind of habit, which enables them to live on the sandy shores and dunes. Look at all the plants you can find on the sand-hills, and you will see that in some way they have their parts adapted to suit the conditions. Very long roots and a running stem are the commonest characters, and these you will find on almost every plant you try to dig up.

Fig. 146. A small piece of the underground stem of Carex, with tufts of leaves coming above the level of the sand; (s) stem, (r) roots (cut off) with small side roots, (sc.) scale leaves underground.

Sometimes the stem can grow up and up, even though it is continually buried by the shifting sand, as you can see very well in the case of the sea holly. You may dig for more than a dozen feet before you come to the end of the vertical stem of what seemed to be quite a small plant (see fig. 147).

Fig. 147. Sea Holly, showing the plant at the surface, and the long stem below the level of the sand (s).

Along the shore are other plants of quite a different kind, which have also special characters to help them to conquer a region which seems to be very inaccessible to land plants. Many curious plants live in the mud-flats that are frequently covered by the tides, and which can therefore only get salt water. You remember that salt kills ordinary land-plants, so that these must be specially built to be able to stand it. Most of them have very thick, fleshy leaves, and rather bushy stems, while others have leathery leaves covered with a kind of wax, or with hairs, which make them look grey. Look at the sea-daisy, and you will see that the leaves are very thick and juicy; so are those of the sea-blite and salt spurry. The boldest of all these plants, the marsh samphire, which goes furthest out to sea, and may grow on bare mud covered by every tide, has not leaves at all, but very thick, fleshy stems, which are green and do the work of leaves (see fig. 148).

Fig. 148. Marsh Samphire or Glasswort, a plant with swollen green stems which do the work of leaves.

All these forms must remind you of the plants which were characteristic of dry regions; how is it that these plants, often actually growing in the water, should yet be specialised in the same way? It is because all the water they get is salt, and it is very difficult for them to live in it. They can only use a relatively small quantity, otherwise they would be forced to take in too much salt, so they must prevent their leaves from transpiring much and using the water up. In this way they are really in the same kind of position and so require to have the same kind of leaves as a plant growing where very little water of any kind is to be had. They are in the same difficulty as the Ancient Mariner, with “Water, water everywhere, nor any drop to drink.”

Pull up a marsh samphire, and you will see that it has a very much branched, spreading root, which gives the plant a firm grip on the sand or mud, but it has not long roots like the sand-dune plants, for all the water which it can use is to be had quite easily and is near at hand.

You may notice, too, on these mud flats the mingling of plants from land and sea. When the marsh samphire and sea-daisy invade the flats which are covered every day by the tide, they are entering the region of the sea-plants, and you may find them growing side by side with the true seaweeds, and even in some cases we may notice the bladderwrack seaweed further in toward the shore than the samphire, which has ventured far out to sea.

As you will find in everything in nature, it is always difficult to draw a fixed line and say that on one side lies one type of thing, and on the other side something different; so, in dealing with different “plant associations,” we find that they have their special regions, but that they tend to cross over any limiting lines set between them. In deep water and on high, dry land, we find quite different kinds of plants which never mix with each other, but on the border land between such regions the boundary is not strictly kept, and we sometimes find plants growing where we might expect the conditions to be unsuited to them.

PLATE VII.

BLADDERWRACK GROWING ON THE ROCKS EXPOSED AT LOW TIDE.

CHAPTER XXXII.
IN THE SEA

All the plants which grow in the sea are hastily grouped together by most people under the name “seaweeds.” We know that there are many kinds of seaweeds, and yet even to one who has not studied them, they do not seem to differ so much from each other as to deserve special classes. And this general view is quite a correct one, for with very few exceptions, all the plants which actually live in the sea are algæ, and so belong to the simplest family of plants (see Chapter XXVII.). Yet they are not without interest and individuality. In the sea these simple plants have everything to themselves; and it is there that we get them developed in a very special way.

You must have noticed that you never find seaweeds actually rooted in the sand (except in protected marshes, where the sea samphire and some flowering plants may grow), because sand is always shifting and being churned up by the waves, so that they cannot get a firm hold. This is almost the same on the pebbly shores where the stones are rolled over by the waves, and so would batter any unfortunate plant growing on them. If you go along a rocky coast at low water, however, you will find countless true seaweeds, growing so thickly that the rocks are covered by their slimy masses, while in the rock pools are beautiful tufts of more delicate seaweeds of all colours (see Plate VII.).

Examine a single plant of bladderwrack or fucus, and pull it up if you can. You will find that it is very slimy and slips out of your fingers, and then, that when you have got a firm hold on it, it sticks so fast to the rocks that it is difficult to get it off without breaking it. Does this mean that it has roots which go right into the rock as the roots of land-plants go into the soil? Find a plant growing on a small stone, if possible, and look closely at it; the “root” does not go into the stone at all, but is much divided and clasps round it, bending into every little crevice and sticking tight. Note, too, that there are no root hairs as there are in land-plants, which is natural enough when the whole plant is growing in water, and can therefore absorb it through all its surface. All that is required from the “root” is that it shall hold firmly on to the rocks and keep the plant from being dashed on to the shore by the waves. The “root” is not a true root, but is really only a part of the simple body, which is specially adapted for attachment.

The many large bladders on the plant are filled with air, as you will see if you split them open, and they help to buoy it up in the water. Notice, too, how flat the whole plant is; it is really a single sheet of tissue or “thallus,” which is much divided, but does not branch in many directions as a land-plant does. All these characters are those of the simple family of algæ, to which all the seaweeds belong. Though in some cases they may form what look like very complicated structures, yet they are always built upon these simple lines.

Often you may find little plants growing on the bigger ones; sometimes a well-established weed may be almost covered by small seaweeds of many kinds, brown, green, or red. These attach themselves to the big plant in much the same way as they would to a rock, but only use it as a place of anchorage, and do not tap its food supply, as the parasitic mistletoe does to the land-plants. In the same way you may find numbers of seaweeds planted on shells or growing on the backs of crabs.

As the tide goes out it gradually exposes the rocks and pools with their innumerable inhabitants. Now in the case of those which are first uncovered, a long time must pass before the water returns, while those quite near the low water level are only uncovered for a little while. Follow the falling tide some day, and look for the effect which this difference (in the time for which they are exposed) has on the plants growing at different depths.

Fig. 149. The Laminarias, which are only exposed at quite low water.

As you go out towards the low water mark you will find first and commonest the bladderwracks, which get more luxuriant where they are a little removed from the region of the pounding waves at the actual shore. Then further out you will find that the bladderwrack gives up its place to another plant very like it, but with more jagged margins. Beyond this you will come to the big strap-shaped laminarias, which never grow where they are very long exposed without water (see fig. 149).

These different regions of seaweeds (some of which are only laid bare by the tides which go very far out) really depend on the fact that the different levels of the shore are left exposed for varying lengths of time according to their depth. If the shore is flat or gently sloping, then the tide has a very great distance to recede before the same depth is reached as would be attained much nearer in where the shore slopes steeply (see fig. 150). This explains how it is that in one place you may have to walk out a quarter of a mile till you come to the region of laminarias, while in another you need walk no distance, but merely clamber down the rather steep rocks to get to it. But as the actual time taken by the falling tide is the same in both cases, the plants at any level are left exposed for almost the same time whatever the kind of shore may be.

Fig. 150. A diagram to show how the slope of the shore influences the distance the tide goes out, and, therefore, the distance from high-water mark at which the different seaweeds grow. A, a gently-sloping shore; B, a steep shore. The line H indicates the high-tide level, and L the low-tide level.

One thing that may perhaps puzzle you about the seaweeds is their colour; some few of them are green, but most are blackish, brown, or even red. How then do they build their food? It is found that true chlorophyll is present as well as the other colours, and that though they hide the green tone from our eyes, they do not hinder its activity in the plant. You can see that the brown bladderwrack is really a green plant if you soak some of its tissues in hot water; the brown colour will be washed out and will leave the plant bright green. In almost all cases these simple algæ living in the sea are self-supporting plants, which have adapted themselves to the special conditions in the depths of the sea where no flowering plants can live, and there they reign supreme.

CHAPTER XXXIII.
PLANTS OF LONG AGO

When we were on the moors we noticed that we may sometimes find plants being actually turned to stone under our eyes (see p. [156]). These are plants which are living at the present time, but this same thing has also happened to plants which lived long ago, and which otherwise we could not see and study, because they are all dead. In those cases in which they did not decompose in the ordinary way after death, but were turned to stone, we are sometimes able to find out almost as much about them as we can about the plants living to-day.

Fig. 151. Plant which was living at the time coal was made, pressed in a stone and so preserved.

You must have seen in museums, or even found for yourself in stones, the remains of leaves and stems of plants which, too, are turned to stone, but which yet show the shape and form of the plant with great beauty. If you go to the north of England, where there are many coal-mines, you will have a good chance of finding pieces of stone which have been thrown out from the mines as refuse, and which have in them or on them most beautiful leaves of ferns and other plants. We know from geologists that these rocks are very old indeed, older than the valleys and downs of the south of England, yet we can see to-day what the plants which lived then looked like, because they have been turned into stone and kept for us in the rocks till the miners dig them out when digging the coal.

Fig. 152. Fern which was living at the time of the coal, pressed between sheets of stone.

But what is coal itself? You know that it is not at all like an ordinary rock, for it burns as well as wood, and has been found to be largely made of carbon. Even directly on top of the coal, and sometimes actually in the coal seams, we find plants preserved, and geologists and botanists have combined to prove that coal is really entirely composed of the crushed remains of ancient plants.

You will remember that we found that many of the plants in the peat bogs did not get decomposed entirely because of the preservative peaty acids present in the water and soil. Something of the same kind happened to the plants of the old forests which now form our coal. As they died they did not entirely decompose, but got pressed tightly together, all their living juices being squeezed away till little but the carbon in them remained. These masses of plants gradually sank beneath the sea, were covered by sandstones and limestones, and were preserved between the beds of rock, forming masses nearly as firm as the rocks themselves. These old plants, which to-day act as our fuel, are really “as old as the hills,” for they were growing in the country before the hills were made.

Fig. 153. The trunk, A, of a fossil tree turned into stone, still standing in the position in which it grew. It is surrounded and covered by the pressed masses of plants (coal) C, fine mud (shales), O, and sandstones, S. Its roots, R, are still in the clays, U, in which they grew, which are now hardened to rock.

As well as the many plants which were preserved in this way, and in which we can now see little but masses of carbon, there were others which were preserved in stone, sometimes pressed between the layers of stone as you press a flower between sheets of blotting-paper, in other cases turned directly into stone without crushing, so that they show their complete form, cell by cell. It is from these stone plants that we learn what the plants of the coal were like. Sometimes we find great trunks of trees standing petrified together in the positions in which they were growing, with their roots twining round one another, and entering the muddy soil on which they lived. Sometimes such tree-stumps stand up through the coal-beds and rocks which must have been deposited all round them (see fig. 153). We find also leaves and stems, cones and seeds, in the stones, till we can build up completely the form and life history of several of the plants which were then living. But in all the wealth of material which has been found, no flowers have ever been discovered. The seeds seem to have belonged to plants of the pine-tree family, so that these old forests were without any of the plants which are to-day the most important family of all, that is, the flowering plants. They lived so long ago that flowers had not come into existence by that time.

Another strange thing about these forests is, that although there were great trees in them, they were not like those of our present forests. To-day our trees are chiefly flowering plants, such as oaks, limes, and beeches; but the giants of these ancient forests were club-mosses and horsetails, plants belonging to the fern tribe. Their descendants, the club-mosses and horsetails growing now, have degenerated, and are humble plants not more than a few feet high at the most, and always of little real importance in the landscape.

The true ferns then living seem to have been more like those of the present, though perhaps a little larger and more important. In the family of ferns then living were some with strange histories, and among the ferns which you may find in the stones some leaves may have belonged to a plant which was truly a “missing link” in the history of plants, and helps us to see the relationship between ferns and pines.

Many and strange are the tales the fossil plants can tell us of the life in the forests when the coal was made, and just as, in the moors, only those moss-plants which were turned to stone will still be there after centuries have gone by, so it was in the old coal-forests that only the plants which were turned to stone remain to tell us their story to-day. For this reason our knowledge of the forests of long ago is not complete; but even now it is enough to tell us something of the life of the plants which were then doing the food-building work of the world. Though the individual plants were so different, the “associations” were in a general way the same as those now living. Great trees reared their heads into the air, and below them, or climbing round and over them, the smaller plants found place long ago as they do to-day.

CHAPTER XXXIV.
PHYSICAL GEOGRAPHY AND PLANTS

If we examine the plants of any district, we find that a number of outside influences affect them very greatly. The most important of these are the physical geography and geology of the place. The form and nature of the rocks and soil, as well as the climate, have a great effect on the plants growing in any spot.

You can see this in an extreme case if you imagine yourself up in a balloon looking down on England as on a map. In certain places you see lakes, that is to say, the rocks and soil are so arranged that they form a basin and hold the water permanently there. Now in a lake, as you know, only water-plants will be growing, so that the presence of a fairly deep and constant lake makes it quite certain what kind of plants must grow in that spot. Imagine an earthquake or some slower earth-movement which is strong enough to change the rocks so that the water all runs away, and the result is that there will be dry land in the same spot where before was the lake. This will cause the water-plants to die sooner or later, and land-plants will replace them.

There is continual change in the arrangement of lakes and rivers, hills and shores, which takes place all around us, but so slowly that we do not notice it. It is slow, and therefore there is not a sudden killing off of any one kind of plant, and a rapid incoming of a different set of plants, but it causes a gradual shifting and moving of the groups among themselves. Sometimes there may be some swift and sudden change, as the result of a landslip or volcano, or in a stream or lake which has been artificially drained, which shows us a very good object-lesson in plant geography.

The importance of the physical form of any place, however, does not only lie in the position of its lakes and streams and the size of its hills. The kind of rock, and nature of the soil covering the rocks, are very important, as well as the many other details of the land.

In England there are no very high mountains, so that you cannot study the effect of great heights on plants, but all the same England affords quite sufficient opportunity for the study of physical geography in its relation to plant-distribution.

Even in the cultivated fields, where man tries to help the plants to overcome their surroundings, you will find the influence of the soil is very largely felt. Ask any farmer about his land, and he may tell you that a certain one of his fields is specially good for potatoes, another for barley, or that in a village a few miles away they can grow splendid crops of strawberries, while his are not worth the planting. Then think of the different kinds of plants for which the different counties of England are noted. No one could get the produce of the cherry orchards and hop-gardens of Kent to grow on the Yorkshire moors. Nor do we find acres of heather moor on the downs in the south of England, but instead there is a short turf with many little flowers which love the chalk and limestone, such as the blue and white polygala, rock roses, and several small orchids.

Now what is the difference between the north and the south of England? It is chiefly one of rock and soil. On the Downs in the south you find a thin coating of brown earth over thick masses of white chalk through the surface of which the water supply quickly runs, so that we get few streams or bogs. In the north the hills are built of coarse sandstones, hard grey limestones, and fine black shales which hold much water, so that there are many swampy places and innumerable streams and little waterfalls. Then, again, the land in the north of Kent, which is so famous for its cherries and hops, is a rich, fine clay, with a muddy and sandy soil, which centuries ago was the bed of a great river, and now is the most important factor in making Kent one of the most fertile parts of England.

If we find that the influence of the physical nature of the land is so strong even in the case of cultivated plants, which are helped by man’s knowledge, we shall expect to find that it is still more felt by the wild plants.

Let us go, for example, to the moors east of Settle, in Yorkshire, where you find the three kinds of rock, the hard limestone, coarse sandstone, and soft, black shales. If you walk across the moors, you will see that the principal plants are heather, bilberry, and several coarse grasses, which grow in more or less irregular patches. If you notice the grasses carefully, you will find that they are of several different kinds, showing varieties in their size, form of leaf, colour, and so on, and that very frequently the different kinds grow on the different types of rock beneath them. After a little experience, you will almost be able to tell what is the nature of the rock on which you are standing by the appearance of the plants at your feet.

If you live anywhere in the south of England, walk over some part of the downs till you see below you in the valley a clay-pit or pottery factory, which shows you that the chalk is no longer under the surface soil, but that it has been replaced by clay. Walk straight towards this place, collecting the plants you meet on the way. On the actual downs you will find many which do not grow near the clay-pit, since they are special chalk lovers. In the clayey valley it is very likely that you may find a pond; if so, walk towards it, noting all you pass on the way. As you get to the edge, reeds and bulrushes, water forget-me-not, tall spikes of water loosestrife, and many others appear which you would have been astonished to meet with on the downs.

Fig. 154. A recently formed pond in Delamere with a dead forest tree standing up in the middle.

A very important factor also is the amount of rain which the district gets. This tells particularly among the ferns and mosses. Along the hedgerows of Kent, for example, where it is rather dry, true ferns will seldom grow, while in Devonshire every hedge and bank has many hundreds of the common polypody fern and the hartstongue. When we come, however, to consider on what it is that the rainfall depends we find that it is the structure, size, and relations of the land masses to the sea and the winds. In fact, it depends on the physical geography of England as a whole. So that in the end the plants and the physical nature of any place are so much in touch that it is almost impossible to do anything in the study of plant distribution without considering physical geography.

Fig. 155. A recently formed pond which has covered a large area of the forest and killed many of the trees. Notice the dead trunks standing and lying about, and the rushes growing near the edge, which would not have been there but for the coming of the water.

Although the changes in physical geography which made and unmake continents are slowly acting around us all the time, it is not often that we can clearly see them taking effect. Photos 154 and 155 are therefore particularly interesting, for they show one of the processes at work. Part of a forest is in the actual course of being killed by the pond which is forming on sinking land. This pond and several smaller ones of the same kind can be studied in the neighbourhood of Delamere forest, in Cheshire. Here the under soil gets washed out in certain places, and the surface earth sinks and forms a hollow in which water collects. In fig. 154 you see one tree standing in the middle of the pond. It is dead, and has been killed by the water (you remember that ordinary plants are drowned by too much water) and in fig. 155 you see a large area entirely covered with water, and the dead trees standing up through it. This pond is spreading rapidly, and is a good illustration of the reverse condition from that seen in fig. 144, where the plants by their growth are filling up a pond. The washing out of the soil and the collecting of the water in this case was quite beyond the control of the plants themselves, but they are supremely affected by it.

CHAPTER XXXV.
PLANT-MAPS

In the last chapter we noticed a few of the many facts which show us that a close relation exists between the plants and the nature of the land on which they grow. We may now try to express these facts in a simple way by making maps of the land according to the plants growing on it.

There are maps of the whole of England, made by the Government, which show all the roads and houses, the chief rocks, hills, ponds, and so on. The geologists have taken these maps and added to them details of the kinds of rock and soil of which the land is built. If now we take fresh copies of the “ordnance” maps, as they are called, and put on them all the plants growing in different associations, we can compare the resulting “plant-maps” with the land-maps of the geologists, and I think you will be surprised to find how much the plant-maps and land-maps correspond.

To do this on a large scale, however, is far too big a piece of work for one person, or a few people, to attempt. We can only do some small piece of work on one area which will show how the rest is done, and yield some interesting details.

Let us suppose, for example, that the moor east of Settle is to be mapped. First get an ordnance survey map on a large scale—25 inches to the mile is the best, but the 6 inches to the mile will do. On the map are marked all the walls, streams, and even some of the bigger trees, so that it is easy to find on it the exact spot where you are standing. For working you should cut the sheet up into at least eight pieces, of regular size and shape, and use one of these at a time in the field.

First get to know the part you are to work on later in a general way, noting the chief plants and in what way they are associated.

Be careful in working to keep your sheets in regular order, and begin with the one at the bottom left-hand corner of the whole map. Find the exact spot on the ground which is represented by the point of the bottom left-hand corner of your first sheet, and put a white stake into it at least two feet high; it is better if you add a little red and white flag, so that you can see it from a distance. Then find each of the other four corners of your small sheet, measuring the distance from a wall or tree if need be, and put in each a white stake similar to that marking the first corner. If your map is on the 25-inch scale, and you have cut it into sixteen equal pieces, you will find that the area staked out on the ground represented in one piece is not so large but that you can see over it, and by walking about within it, get all the features of the plants growing there mapped out on to your sheet. In studying the different patches of plants, you will find that, as a rule, in each there is one important plant which grows in great numbers, while there are many more scattered and less important species growing with it. Such patches of plants growing together may be called Associations, and in mapping we only pay attention to the chief of these. In a patch where cotton-grass is the most conspicuous thing, there may be also half a dozen small grasses and plants growing with it, in which case everything but the cotton grass would be ignored in the mapping, and the association called the “cotton grass” association. Similarly, a patch where heather is the most important plant would be called the heather association. Sometimes you may find two or more plants growing together which seem to share the area between them, so that it is impossible to tell which is the chief one; in such a case where, for example, heather and bilberry are apparently equally important, the association would be described as “heather-bilberry.” For the sake of reference, lists should be kept of all the plants of less importance growing in the associations, though they are ignored in the mapping.

At the beginning it is wise to go over the area and find out roughly how many chief associations there are in it, and to make out a list of them. Then choose either a colour or a sign to represent each of them in the mapping,—a colour will generally be found to be clearer and more effective in the finished map, though a sign is very useful for the field-work.

When all these preliminaries are finished, begin the actual mapping by going very carefully over the different patches in the staked-out area of one piece of the sheet. From the details already printed in the ordnance survey map, you will generally be able to find the exact position of the patches of plant associations (unless they are very small, when they must be ignored), and you should soon be able from the help of the given details to fill in the shape of the patches by the eye. If in any case this is difficult, a 5-foot rule and a string of 20 feet or 30 feet marked out into 5 feet and 1 foot lengths will be found very useful. From the actual measurements you will then get, it is easy to find how much will represent them on the map by the simple sum:—1,760 actual yards are represented by 25 inches on the map, so that 16, 10, or whatever number of feet you require will be represented by (25 in. x 10 in.)/(1,760 x 3) or (25 in. x 16 in.)/(1,760 x 3) and so on.

Do all your field-work in pencil, and take notes in a “field-book” as you go, so that you will be able to copy out a neat, correct map at home in which to colour in the associations and outline the patches with waterproof ink. When one of the sheets is done in this way, stake out the area for the next, and so on, till you have all the sheets finished. Then paste them together again on a piece of muslin in their proper order, and you will have a complete “plant-map” of one definite, though small, area. This can be easily compared with a geological map of the same area, though the geological one will be on a rather smaller scale (best 6 inches to the mile), and you will see how the patches of plants frequently follow the arrangement of the rocks. This does not show so clearly on too small an area; the larger the district you can cover the better.

To work from an ordnance survey map is the easiest way of proceeding, but if you like to combine the plant study with a little simple survey work, it is quite possible to make the map from the very beginning. This is not generally worth the trouble, except in cases where you find a rich and interesting area which would repay very careful mapping on a larger scale than the survey have published. For example, it would be a very good plan to choose some small area, and in it stake out exactly 100 feet square. Along the sides plant smaller stakes every 20 feet, and map all the details very carefully on to mathematical paper on the scale of either 5 inches or better, 10 inches to 100 feet. Such an area would well repay the trouble of repeated mapping at different times of the year. If you have a series of maps of the exact area every two months, for example, you will be able to see from them very well the succession of plants throughout the year, and how the associations change according to the seasons.

Another thing that should go with the mapping is the plotting out of “sections” through the irregular land, which will show clearly how frequently the plants growing on any spot are determined by the level of the spot and its consequent relation to the water supply. The most striking case of this kind is that of a section through a pond or stream and its banks. Unless you have a boat at your service, you will have to choose a stream where two people can meet across it from the banks, or else content yourself with going out only as far as you can wade.

To begin the “section” you should choose a good place where there seems to be plenty of variety in the plants; then fix a strong stake into the water as far out as you intend to go, tying on to it a string measured out into 1-foot divisions. This string should be 20, 30, or more feet long, according to the kind of edge the pond has, and its other end should be fastened to a stake also.

Fig. 156. A “section” of the edge of a pond plotted out on mathematical paper. a-b, the level of the water. A-B, a line parallel to it, marked by a measured string fastened to stakes, from which the measurements are taken.

Take the dry land where ordinary land-plants are growing as your starting-point, and fasten your string to it, as in (B) fig. 156, making it level on your stake in the water (A) if possible, so that the same string can be used to take measurements and levels from.

As you work measure the actual distance along the string, and the depth from the string of each variety of plants, and where there are few, of each individual plant crossed by the string. When you come to plotting this out on mathematical paper you will require to reduce the scale by letting two small squares of the paper represent an actual foot, or whatever seems to be convenient. Then from your actual measurements you can soon plot out a “section” of the pond, e.g., in actual measurements the bulrushes were growing 1 foot below the water surface, that is, 4½ feet below the fixed level, and the first was 6⅔ feet distant from the stake in the water. In plotting you should represent the actual plants by symbols or simple signs, as is done in the figure, so as to be able to see at a single glance just how everything was arranged. Note also the level of the surface of the water, which you may choose as your working level if you prefer it to the line given by A-B.

From this you will see very clearly how extremely important is the amount of water in determining what kind of plant is growing in any given spot.

After having done these small pieces of mapping, other problems will suggest themselves to you, and you will find that the work of making maps and plans of the plants is more than repaid by the facts you find out from the plants themselves, and the insight you get into some of the rules which guide the plants in their choice of their homes.

CHAPTER XXXVI.
EXCURSIONS AND COLLECTING

When you plan an excursion do not take your collecting tin and a “Flora” in which to look up the names of all you find, and then imagine that you are fully prepared for a day’s botanising. It is, of course, a very useful thing to learn the names of the flowers you find, because you cannot even speak of a plant if you do not know its name, but the mere naming is in reality the least interesting and important thing about them, as you will know if you have followed the study of plants in the way suggested in this book.

In arranging an excursion, or what is far better, a series of excursions into the country, the most important thing to have is a plan of action. Do not wander aimlessly in the woods, attracted from side to side by all that comes in your way; choose rather some special set of things to collect and study. If there are several of you together, then each one should have a particular subject about which to make notes and collections; then afterwards all the members of the excursion party should meet together and compare their results, and show each other any interesting specimens obtained.

Each person should be provided with:—A tin collecting-box, a strong knife or digger, a note-book, pencil, and magnifying-glass, some string, and a fine knife.

In case you find it difficult to decide on special things to do, here is a list of a few of the many suitable subjects which may be chosen. The list is not at all complete, but it may give you a few ideas at the beginning of your field-work.

1. In the early spring, study particularly all the plants which are flowering. Dig up complete specimens of all the smaller plants, and notice how many of them have some special means of storing food underground through the winter, such as bulbs, tubers, and so on. This stored food makes it possible for the flowers to bloom before the leaves have done any work, a thing which would be impossible in the case of ordinary young plants. Our “early” spring flowers are really late flowerers, as they bloom on the result of the food made in the previous year. Make drawings, or press a series of these.

2. Collect buds and opening buds, getting series of scales from the outer hard ones to the inner developed leaves, and press them.

3. Notice, and make sketches of, the different ways in which leaves are folded in buds: the fan-like beech, the coiled fern, and so on.

4. Collect seedlings; notice specially those of trees. Study the form of their earlier leaves, which are generally simpler than the mature ones.

5. In summer, collect as many forms as possible of full-grown leaves. Compare and classify them according to their nature and shape: those which are simple or compound, and then in more detail. Dry and mount a series of representative ones.

6. Study very particularly flowers in relation to their insect visitors. For this it is better to remain a long time in one place, so that it is not so good for a general excursion, but is splendid if you can get off for an early excursion by yourself, or with one or two companions.

7. Make collections and lists of all climbing plants, noting by what means they climb.

8. Keep a list for the whole year of the colours of the flowers as they come out, noting in general which are the most characteristic for the different seasons.

9. Collect fruits, and arrange them according to the way they scatter the seeds.

10. When the leaves are falling, notice where they break away, and what form of scars they leave. In the case of compound leaves, whether they fall off whole or in parts.

11. Collect series of plants which are growing together in different places, e.g., those in a woodland glade, those at the edge of a pond, those on a sandy hill, and so on. Dry them by pressure between sheets of paper, and mount them, noting how their forms correspond to their surroundings.

12. Go to the same spot in a wood in spring, summer, autumn, and winter; make notes and drawings of what you see each time. In the spring there will be a carpet of flowers under the bare trees, note what happens in the summer, and later on.

---

These suggestions are only a beginning, and special problems will arise of their own accord in connection with the work you are doing, till you find that the real excursion becomes the most interesting and important part of your work. If we go to the plants themselves and ask them to teach us, they will never fail to give us the chance of learning lessons of ever-increasing interest.