NOTABLE PLANT FAMILIES
Although the great majority of plant families can only be distinguished by a combination of characteristics which are too obscure to obtain any general recognition, there are some few instances where these family traits are sufficiently conspicuous to be of great assistance in the ready identification of flowers.
If, for instance, we recognize at sight a papilionaceous blossom and know that such an one only occurs in the Pulse family, we save the time and energy which might otherwise have been expended on the comparison of a newly found blossom of this character with the descriptions of flowers of a different lineage. Consequently it has seemed wise briefly to describe the marked features of such important families as generally admit of easy identification.
Composite Family.—It is fortunate for the amateur botanist that the plant family which usually secures the quickest recognition should also be the largest in the world. The members of the Composite family attract attention in every quarter of the globe, and make themselves evident from early spring till late autumn, but more especially with us during the latter season.
The most noticeable characteristic of the Composites is the crowding of a number of small flowers into a close cluster or head, which head is surrounded by an involucre, and has the effect of a single blossom. Although this grouping of small flowers in a head is not peculiar to this tribe, the same thing being found in the clovers, the milkworts, and in various other plants—still a little experience will enable one to distinguish a Composite without any analysis of the separate blossoms which form the head.
These heads vary greatly in size and appearance. At times they are large and solitary, as in the dandelion. Again they are small and clustered, as in the yarrow (Pl. XXVIII.).
In some genera they are composed of flowers which are all similar in form and color, as in the dandelion, where all the corollas are strap-shaped and yellow; or, as in the common thistle, where they are all tubular-shaped and pinkish-purple.
In others they are made up of both kinds of flowers, as in the daisy, where only the yellow central or disk-flowers are tubular-shaped, while the white outer or ray-flowers are strap-shaped. The flower-heads of the well-known asters and golden-rods are composed of both ray and disk-flowers also; but while the ray-flowers of the aster, like those of the daisy, wear a different color from the yellow disk-flowers, both kinds are yellow in the golden-rod.
If the dandelion or the chicory (Pl. XCVIII.) is studied as an example of a head which is composed entirely of strap-shaped blossoms; the common thistle or the stick-tight (Pl. LVIII.) as an example of one which is made up of tubular-shaped blossoms; and the daisy or the sunflower (Pl. LVII.) as an example of one which combines ray and disk-flowers—as the strap-shaped and tubular blossoms are called when both are present—there need be little difficulty in the after recognition of a member of this family. The identification of a particular species or even genus will be a less simple matter; the former being a task which has been known to tax the patience of even advanced botanists.
Mr. Grant Allen believes that the Composites largely owe their universal sway to their “co-operative system.” He says: “If we look close into the Daisy we see that its centre comprises a whole mass of little yellow bells, each of which consists of corolla, stamens, and pistil. The insect which alights on the head can take his fill in a leisurely way, without moving from his standing-place; and meanwhile he is proving a good ally of the plant by fertilizing one after another of its numerous ovaries. Each tiny bell by itself would prove too inconspicuous to attract much attention from the passing bee; but union is strength for the Daisy as for the State, and the little composites have found their co-operative system answer so well, that late as was their appearance upon the earth they are generally considered at the present day to be the most numerous family both in species and individuals of all flowering plants.” While those of us who know the country lanes at that season when
—ranks of seeds their witness bear,
feel that much of their omnipresence is due to their unsurpassed facilities for globe-trotting. Our roadsides every autumn are lined with tall golden-rods, whose brown, velvety clusters are composed of masses of tiny seeds whose downy sails are set for their aerial voyage; with asters, whose myriad flower-heads are transformed into little puff-balls which are awaiting dissolution by the November winds, and with others of the tribe whose hooked seeds win a less ethereal but equally effective transportation.
Parsley Family.—The most familiar representative of the Parsley family is the wild carrot, which so profusely decks the highways throughout the summer with its white, lace-like clusters; while the meadow parsnip is perhaps the best known of its yellow members.
This family can usually be recognized by the arrangement of its minute flowers in umbels (p. [9]), which umbels are again so clustered as to form a compound umbel (Wild Carrot, Pl. XXVIII.) whose radiating stalks suggest the ribs of an umbrella, and give this Order its Latin name of Umbelliferæ.
A close examination of the tiny flowers which compose these umbrella-like clusters discovers that each one has five white or yellow petals, five stamens, and a two-styled pistil. Sometimes the calyx shows five minute teeth. The leaves are usually divided into leaflets or segments which are often much toothed or incised.
The Parsleys are largely distinguished from one another by differences in their fruit, which can only be detected with the aid of a microscope. It is hoped, however, that the more common and noticeable species will be recognized by means of descriptions which give their general appearance, season of blooming, and favorite haunts.
Pulse Family.—The Pulse family includes many of our common wood- and field-flowers. The majority of its members are easily distinguished by those irregular, butterfly-shaped blossoms which are described as papilionaceous. The sweet pea is a familiar example of such a flower, and a study of its curious structure renders easy the after identification of a papilionaceous blossom, even if it be as small as one of the many which make up the head of the common pink clover.
The calyx of such a flower is of five more or less—and sometimes unequally—united sepals. The corolla consists of five irregular petals, the upper one of which is generally wrapped about the others in bud, while it spreads or turns backward in flower. This petal is called the standard. The two side petals are called wings. The two lower ones are usually somewhat united and form a sort of pouch which encloses the stamens and style; this is called the keel, from a fancied likeness to the prow of an ancient vessel. There are usually ten stamens and one pistil.
These flowers are peculiarly adapted to cross-fertilization through insect agency, although one might imagine the contrary to be the case from the relative positions of stamens and pistil. In the pea-blossom, for example, the hairy portion of the style receives the pollen from the early maturing stamens. The weight of a visiting bee projects the stigma and the pollen-laden style against the insect’s body. But it must be observed that in this action the stigma first brushes against the bee, while the pollen-laden style touches him later, with the result that the bee soon flies to another flower on whose fresh stigma the detached pollen is left, while a new cargo of this valuable material is unconsciously secured, and the same process is indefinitely repeated.
Mint Family.—A member of the Mint family usually exhales an aromatic fragrance which aids us to place it correctly. If to this characteristic is added a square stem, opposite leaves, a two-lipped corolla, four stamens in pairs—two being longer than the others—or two stamens only, and a pistil whose style (two-lobed at the apex) rises from a deeply four-lobed ovary which splits apart in fruit into four little seed-like nutlets, we may feel sure that one of the many Mints is before us.
Sometimes we think we have encountered one of the family because we find the opposite leaves, two-lipped corolla, four stamens, and an ovary that splits into four nutlets in fruit; but unless the ovary was also deeply four-lobed in the flower, the plant is probably a Vervain, a tribe which greatly resembles the Mints. The Figworts, too, might be confused with the Mints did we not always keep in mind the four-lobed ovary.
In this family we find the common catnip and pennyroyal, the pretty ground ivy, and the handsome bee balm (Pl. LXXXII.).
Mustard Family.—The Mustard family is one which is abundantly represented in waste places everywhere by the little shepherd’s purse or pickpocket, and along the roadsides by the yellow mustard, wild radish, and winter-cress (Pl. XLII.).
Its members may be recognized by their alternate leaves, their biting harmless juice, and by their white, yellow, or purplish flowers, the structure of which at once betrays the family to which they belong.
The calyx of these flowers is divided into four sepals. The four petals are placed opposite each other in pairs, their spreading blades forming a cross which gives the Order its Latin name Cruciferæ. There are usually six stamens, two of which are inserted lower down than the others. The single pistil becomes in fruit a pod. Many of the Mustards are difficult of identification without a careful examination of their pods and seeds.
Orchis Family.—To the minds of many the term orchid only suggests a tropical air-plant, which is rendered conspicuous either by its beauty or by its unusual and noticeable structure.
This impression is, perhaps, partly due to the rude print in some old text-book which endeared itself to our childish minds by those startling and extravagant illustrations which are responsible for so many shattered illusions in later life; and partly to the various exhibitions of flowers in which only the exotic members of this family are displayed.
Consequently, when the dull clusters of the ragged fringed orchis, or the muddy racemes of the coral-root, or even the slender, graceful spires of the ladies’ tresses are brought from the woods or roadside and exhibited as one of so celebrated a tribe, they are usually viewed with scornful incredulity, or, if the authority of the exhibitor be sufficient to conquer disbelief, with unqualified disappointment. The marvellous mechanism which is exhibited by the humblest member of the Orchis family, and which suffices to secure the patient scrutiny and wondering admiration of the scientist, conveys to the uninitiated as little of interest or beauty as would a page of Homer in the original to one without scholarly attainments.
The uprooting of a popular theory must be the work of years, especially when it is impossible to offer as a substitute one which is equally capable of being tersely defined and readily apprehended; for many seem to hold it a righteous principle to cherish even a delusion till it be replaced by a belief which affords an equal amount of satisfaction. It is simpler to describe an orchid as a tropical air-plant which apes the appearance of an insect and never roots in the ground than it is to master by patient study and observation the various characteristics which so combine in such a plant as to make it finally recognizable and describable. Unfortunately, too, the enumeration of these unsensational details does not appeal to the popular mind, and so fails to win by its accuracy the place already occupied by the incorrect but pleasing conception of an orchid.
For the benefit of those who wish to be able to correctly place these curious and interesting flowers, as brief a description as seems compatible with their recognition is appended.
Leaves.—Alternate, parallel-nerved.
Flowers.—Irregular in form, solitary or clustered, each one subtended by a bract.
Perianth.—Of six divisions in two sets. The three outer divisions are sepals, but they are usually petal-like in appearance. The three inner are petals. By a twist of the ovary what would otherwise be the upper petal is made the lower. This division is termed the lip; it is frequently brightly colored or grotesquely shaped, being at times deeply fringed or furrowed; it has often a spur-like appendage which secretes nectar; it is an important feature of the flower and is apparently designed to attract insects for the purpose of securing their aid in the cross-fertilization which is usually necessary for the perpetuation of the different species of this family, all of which give evidence of great modification by means of insect-selection.
In the heart of the flower is the column; this is usually composed of the stamen (of two in the Cypripediums), which is confluent with the style or thick, fleshy stigma. The two cells of the anther are placed on either side of and somewhat above the stigma; these cells hold the two pollen masses.
Darwin tells us that the flower of an orchid originally consisted of fifteen different parts, three petals, three sepals, six stamens, and three pistils. He shows traces of all these parts in the modern orchid.