From the simplest and regular types of flowers, as in the buttercup, we pass on to more and more involved and unsymmetrical forms, as the columbine, monk's-hood, larkspur, aristolochia, and thus finally to the most highly specialized or involved forms of all, as seen in the orchid-the multifarious, multiversant orchid; the beautiful orchid; the ugly orchid; the fragrant orchid; the fetid orchid; the graceful, homely, grotesque, uncanny, mimetic, and, until the year 1859, the absolutely non-committal and inexplicable flower; the blossom which had waited through the ages for Darwin, its chosen interpreter, ere she yielded her secret to humanity.
And what is an orchid? How are we to know that this blossom which we plucked is an orchid? The average reader will exclaim, "Because it is an air-plant"-the essential requisite, it would seem, in the popular mind. Of over 3000 known species of orchids, it is true a great majority are air-plants, or epiphytes-growing upon trees and other plants, obtaining their sustenance from the air, and not truly parasitic; but of the fifty-odd native species of the northeastern United States, not one is of this character, all growing in the ground, like other plants. It is only by the botanical structure of the flowers that the orchid may be readily distinguished, the epiphytic character being of little significance botanically.
A brief glance at this structural peculiarity may properly precede our more elaborate consideration of a few species of these remarkable flowers.
The orchids are usually very irregular, and six-parted. The ovary is one-celled, and becomes a pod containing an enormous yield of minute, almost spore-like, seeds (Fig. 3) in some species, as in the vanilla pod, to the number of a million, and in one species of the maxillaria, as has been carefully computed, 1,750,000.
The pollen, unlike ordinary flowers, is gathered together in waxy masses of varying consistency, variously formed and disposed in the blossom, its grains being connected with elastic cobwebby threads, which occasionally permit the entire mass to be stretched to four or five times its length, and recover its original shape when released. This is noticeable specially in the
[Illustration: Fig. 1]
But the most significant botanical contrast and distinction is found in the union of the style and stamens in one organ, called the column (Fig. 2), the stigma and the pollen being thus disposed upon a single common stalk. The contrast to the ordinary flower will be readily appreciated by comparison of the accompanying diagrams (Fig. 1).
When, therefore, we find a blossom with the anthers or pollen receptacle united to a stalk upon which the stigma is also placed, we have an orchid.
The order is further remarkable, as Darwin first demonstrated in his wonderful volume "The Fertilization of Orchids," in that the entire group, with very few exceptions, are absolutely dependent upon insects for their perpetuation through seed. They possess no possible resource for self-fertilization in the neglect of these insect sponsors.
[Illustration: Fig. 2 a. Anther. s. Stigma.]
Many of our common wild flowers, as perfectly and effectually planned for cross-fertilization as the orchids,
But the orchid has lost such power, and in the progress of evolution has gradually adapted itself to the insect, often to a particular species of insect, its sole sponsor, which natural selection has again gradually modified in relation to the flower.
The above work by Darwin was mostly concerned with foreign species, generally under artificial cultivation, and so startling were the disclosures concerning these hitherto sphinx-like floral beings that a most extensive bibliography soon attested the widespread inspiration and interest awakened by its pages.
But it is by no means necessary to visit the tropics or the conservatory for examples of these wonders. Our own Asa Gray, one of Darwin's instant proselytes, was prompt to demonstrate that the commonest of our native American species might afford revelations quite as astonishing as those exotic species which Darwin had described.
[Illustration: Fig. 3]
