XXIV.
A SPOTTED ORCHIS.
Like Mr. Chamberlain, I too am an orchid-grower. I own three acres (without a cow) on a heather-clad hilltop, and no small proportion of that landed estate is “down under orchids.” Not that I mean to say the species I cultivate, or rather allow to grow wild, on my wild little plot would excite the envy of the magnate of Highbury. They are nothing more than common English spotted orchids, springing free and spontaneous among the gorse and heather. But, oh! how beautiful they are! how much more beautiful than the dendrobiums and cattleyas, the flowering spiders and blossoming lizards of the rich man’s hothouse! How proudly they raise their tall spikes of pale bloom, true sultanas of the moorland! how daintily they woo the big burly bumble bees! how gracefully they bend their nodding heads before the bold south-west that careers across the country! They seem to me always such great regal flowers, yet simple with the simplicity of the untrodden upland.
Take a spike and look at it close; or, better still, grub it up by the roots with the point of your umbrella, and examine it all through from its foundation upward. It springs from two tubers, not unlike a pair of new potatoes to look at, but deeply divided below into finger-like processes. Those divisions it was that gave the plant its quaint old English title of “dead men’s fingers”—for, indeed, there is something clammy and corpse-like about the feel of the tubers; while that “coarser name” to which Shakespeare alludes in passing, is due to their general shape, and is still enshrined in the Greek word “orchid” which everybody now applies to them without thinking for a moment of its unsavoury meaning. But the two tubers are not of the same age. One is old and wilted; the other is young and fresh, and, as the advertisements say, “still growing.” The first is last year’s reserve-fund for this year’s flowering stem; the second is this year’s storehouse of food for next year’s blossom. Thus each season depends for its flowers upon the previous year’s income; the leaves, which are the mouths and stomachs of the plants, lay by material in due season; and the spike of bells proceeds from the tubers or consolidated reserve-fund as soon as the summer is sufficiently advanced for the process of flowering. Few plants with handsome heads or trusses of bloom, indeed, can afford to produce them upon the current season’s income; therefore you will find that most large-flowered forms, like lilies, tulips, hyacinths, and daffodils, if they wish to blossom early in the year, depend for their food-supply upon a bulb or tuber of last season’s making. Only in the orchids, however, do you find this curious device of a pair of tubers at once side by side, one being filled and fed, while the other is being slowly devoured and depleted. By the end of the season the new tuber is rich and full to bursting, while the old one is withered, flaccid, and empty.
From the tuber, in early spring, start the pretty lance-shaped leaves—green, dappled with leopard spots of some deep brown pigment. The use and meaning of these beautiful spots on the glossy green foliage no one has yet deciphered; it remains as one of the ten thousand insoluble mysteries of plant existence. That is always so in life. We tell what we know; but what we know not, who shall count it or number it? Yet the flowers, after all, are the true centre of interest in the English orchid. Thirty of them in a spike, pale lilac or white, all starred and brocaded with strange flecks of purple, they rank among the most marvellous of our native flowers in shape and structure. The long spur at the back is the factory and reservoir for the abundant honey. The face of the blossom consists of a broad and showy lip, the flaunting advertisement to bee or butterfly of the sweets within; it is flanked by two slender spreading wings, above which a third sepal arches over the helmet-like petals. Beneath this hood, or dome, in the centre of the column, the club-shaped pollen-masses lie half concealed in two pockets, or pouches—dainty little purses, as it were, like fairy wallets—slit open in front for the bee’s convenience. The base of the pollen-masses is sticky or gummy; and they are so arranged, of set purpose, in their pouches, that the moment the bee’s head touches them, they cling to it automatically, by their gummy end, and are carried off without his knowledge or consent to the next flower he visits. But if you want to see exactly how this pretty little drama of plant life is enacted, you need not wait, as I have often done, silent on the heath for half an hour together, till some blustering bumble bee bustles in, all importance. It suffices for demonstration just to pick a spike and insert into the mouth of the honey-spur a stem of grass, which does duty for the bee’s head and proboscis, when straightway “the figures will act,” as they say on the penny-in-the-slot machines, and the pollen-masses will gum themselves by automatic action to the imaginary insect.
The reason for this curious and highly advanced device is that orchids are among the plants most absolutely specialized for insect-fertilization. Most species of orchid, in fact, can never set their seeds at all without the intervention of these flying “marriage priests,” as Darwin quaintly called them. If left to themselves, the flowers must wither on their virgin thorn unwed, and no seed be set in the twisted ovary. But when the bee goes to them in search of honey, the pollen-masses gum themselves to the front of his head, though just at first they point upward and inward. Then, after a short time, as he flies through the air, they contract in drying, and so point forward, in the direction in which he will enter the next flower he visits. This brings the pollen directly into contact with the sensitive cushion or pad of the ovary in the flower so visited, and thus results in the desired cross-fertilization. For the ovary, too, is gummy, to make the pollen stick to it.
A roundabout way, you think, to arrive, after all, at so simple a conclusion? Well, that is the habit of Nature. And again, bethink you, good, easy-going human being, how great are the difficulties she has to contend with, especially in the case of the plant creation. Put yourself in the orchid’s place, and you will see the reason. For remember how absolutely fixed and limited are plants, each rooted to the soil in a single small spot, each tied by strict conditions of rock, and water-supply, and air, and wind, and sun, and climate, from which none can escape, try they all their hardest. The opposite sides of a road are to them as the two poles, one with a sunny and southward-looking bank, the other with a cold and forbidding northern aspect; so that what flourishes apace on the first would shiver and die of chill winds on the second. Remember, too, that, save in the mildest degree, plants have no power of spontaneous or independent movement; they cannot stir from their birthplace, were it but for a single inch, nor move their own limbs save as the wind may sway them. Creatures thus narrowly and inevitably bound down must needs take advantage of the power of movement in all other kinds, wherever it will benefit them. Hence the use plants make of insects as common carriers of pollen; the use they make of birds as dispersers of seeds; the use they make of natural agencies, such as wind or stream, to waft winged thistle-down, to carry the parachutes of the dandelion and the willow, or to float the male blossoms of such water-weeds as vallisneria. Behold! I show you a mystery. The secret of the whole thing is that plants, being fixed themselves, must needs employ birds and insects as their Pickford vans—must rely on wind or stream for such casual services as wind or stream can easily afford them. Only in a few species can they effect anything like active movement for themselves, as one sees in the rooting runners of strawberries, or the wandering tubers of certain vagrant orchids, which spread far afield from last season’s nesting-place. These are clever devices for securing fresh virgin soil—“rotation of crops,” as the farmers put it.
XXV.
THE ROOT OF THE MATTER.
Every Girton girl (vice Macaulay’s schoolboy, retired from overwork)—every Girton girl knows that a well-conducted British oak “spreads its roots as far and wide through the soil beneath as it rears its boughs above toward the air of heaven.” Every Girton girl is probably also of opinion that the British oak does this mainly or solely in order to fix itself by firm anchors in the soil—to withstand the battling winds and the constant pull of hostile gravitation. But what every Girton girl does not, perhaps, quite so confidently know is this—that, on the whole, the tips of the roots and the tips of the branches correspond roughly in situation with one another, so that if you were to unearth and expose the entire tree you would find it composed of two tolerably similar domes or hemispheres—one erect and aërial, and one inverted and earth-bound, each occupying approximately equal areas, and each circumscribed by fairly equal circles.
Why should this be so? It is clear enough, of course, that in order to fasten a big tree firmly in the ground, it must have numerous large and strong foundations. But wherefore this approximate equality in the areas occupied by roots and frondage? The answer is, because every large tree forms a sort of umbrella, a domed roof or catchment basin for the rain that falls upon it; and it has always its own peculiar and admirably adapted arrangement for conducting all the water it intercepts to certain special spots or drinking-places in the ground, where it sets the roots, and especially the rootlets, or absorbent terminals, intended to soak that water up and convey it to the branches. If you stand under an oak-tree during a summer shower—a mode of passive scientific observation for which nature has afforded quite ample opportunities during the last few weeks—you will notice at once that the round mass of its foliage acts exactly like a huge umbrella, and conducts all the rain that falls upon its surface outward and downward towards the circumference of the circle. The drops that alight upon the central and tallest part of the tree are shed by the veined and channelled leaves till they fall off the tips on to the layer immediately below and outside them; this layer again conveys them to the next in order, and so on, till at last a little gathering stream drips from the ends of the lowest and longest outward-pointing boughs on to the soil beneath them. The ground in the centre remains perfectly dry, while a circle at the circumference is hollowed into a sort of irregular trench, or rude round of tiny pits, by the continuous dripping of the collected gutters.
Now, of course, the plant wants to utilize to the utmost all the rain it thus intercepts. It would be quite too silly of it to produce rootlets and absorbent terminals in the dry central space covered by the dense umbrella of foliage. But all around the circumference, and especially at the spots just under the runnels, where the water drops from the ends of the boughs, exactly as it drops from the rib-points of the silk-and-steel umbrella, the tree develops numerous minute rootlets, which suck up the rain as fast as it falls, and convey it by fixed pipes to the leaves and growing-points. Every tree and every large herb is thus a regular and well-organized catchment-basin, with its own mains and services; and it utilizes its water-supply by a cunningly adapted system of sucking rootlets, all placed at the exact spots where they will most surely absorb the amount of water that in each case runs down to them. So much is this true that in transplanting trees foresters and nurserymen know well you must lop the roots and the branches so as to cover equal superficial areas, or else the water will not fall on the parts best adapted to receive it; for, just as the lopped branches put forth new leaves and twigs at the point of section, so do the lopped roots put forth new rootlets and absorbent hairs at the place where they are now most urgently needed.