Orchids, a large family of plants (orchida-cece), the typical genus of which is orchis (the ancient name of the plant). Popularly any plant of the family, of whatever genus, is called an orchis. The orchids are monocotyledonous (endogenous), herbaceous plants, differing considerably in their manner of growth; some have their rootstocks thickened to form underground tubers, while others have the bases of their connate leaves, together with the thickened base of the stem, much swollen to form a large above-ground tuber-like body, called a pseudo-bulb. The leaves present a great variety; some are thin and of short duration, others thick, fleshy, and persistent; and while some genera present a broad expanse of foliage, in others the leaves are linear, or long and cylindrical, like a piece of whip cord. The flowers are terminal and solitary, or disposed in a raceme or panicle; and the structure in these is so strikingly unlike that in other flowers that a plant of this family is readily recognized. The flowers are six-parted; the three outer parts, corresponding to the calyx, are usually petal-like, and these with the three inner parts, or corolla, are often so unlike in size and shape that the flowers are usually conspicuously irregular; this irregularity is mostly due to one of the three petals, which in the flower appears lowermost; this is called the lip or labellum, and is usually quite dissimilar to the other two petals.
In the greater green orchis (habenaria orbiculata), fig. 1, selected for illustration on account of its simpler structure, the three sepals (1), the upper larger than the other two, are much broader than the petals, two of which are seen (2) pointing upward, while the third, the lip (3), extends downward like a long flat ribbon; in other species the lip spreads out like a broad fan, which is sometimes lobed and beautifully fringed; in others it has its edges turned in to form; sort of tube, or it may be, as in the cypripediums (see Lady's Slipper), distended to form a large inflated sac. It is upon the lip that the most beautiful colors and the strongest markings are displayed, and not only on this account but by its greater size the lip is the most noticeable part of the flower. The base of the lip is frequently hollowed out to form a sac, or is prolonged to form a spur which secretes honey; this in the greater green orchis is very long and conspicuous, it being the club-shaped body (4), nearly twice as long as the lip. In the centre of the flower are the reproductive organs, which in this family consist of one, or at most two stamens, united with the pistil, or rather the style; the two being blended into a column makes the structure at first sight puzzling.
In fig. 1 the column (5) is seen in the centre of the flower, and at 6 it is shown more enlarged; it consists of a large anther united with a concave stigma seen between its widely separated cells. In the majority of the orchids the pollen is agglomerated in two or more pollen masses (pol-linia), in which the grains are held together by minute elastic threads, or are in a compact waxy mass; these pollen masses (7), which are lodged in the cells or pockets of the anther, have often a little pedicel or stalk, at the base of which is a viscid disk or gland (8); this, coming in contact with an insect visiting the flower, adheres to it, and the pollen mass is thus withdrawn from its pouch and carried by the insect to another flower; indeed, the structure is such throughout the whole family, varied admirably in different genera, that the flowers cannot be fertilized except through the aid of insects. As early as 1793 Sprengel showed that the pollen masses in some orchids could only be removed from their lodgment in the pouches by the aid of insects; and Robert Brown in 1833 announced the opinion that insects were essential to the fructification of most orchids.
It remained for Darwin ("Fertilization of Orchids," London, 1802) to present the subject in all its details, to show the wonderfully varied mechanism of the different genera, and to point out the beneficial results from the intercrossing attending this method of fertilization. The relations of our native orchids to insects have been studied by Gray and others, and similar observations have been made upon other plants. (See Insect Fertilization.) In flowers having a structure similar to that of the greater green orchis the act of fertilization is very simple, and may bo imitated by the use of a lead pencil or similar pointed implement. The disk at the lower end of the pollen masses is so exceedingly viscid that when the pencil is thrust into the throat of the flower and withdrawn, like an insect's proboscis, one or both of the pollen masses are brought out with it; the viscid matter quickly hardening and fixing them firmly, as at a, fig. 2. If the pencil were now thrust into the throat of another flower, the pollen mass would not come in contact with the stigma, a difficulty which is overcome in a most wonderful manner.
The stem of the pollen mass is endowed with a remarkable power of contraction, and in about 30 seconds after its dis-lodgment from the anther cell the pollen mass assumes the position shown at b, always bending toward the point of the pencil or the proboscis of the insect; so by the time an insect, with the pollen mass glued to his head or proboscis, can fly to another plant, the mass is in just the position to reach the stigma while the insect is searching for honey. In the greater green orchis, the tube containing the honey is so very long that but few insects have a proboscis sufficient to reach it, and it is thought by Gray that the work of fertilization is done by some of the sphinxes, which have been caught with pollen masses attached to their eyes, as in figs. 3 and 4, from Gray. Fig. 3 gives a side view of the head of the moth as it leaves a flower with the pollinia freshly attached to its eyes, and fig. 4 is a front view of the same head by the time it has reached another plant, the masses having assumed by curving a position which will bring them in contact with the stigma of the next flower the insect explores.
The form and position of the pollen masses in other genera, and the mechanism of the operation, differ widely from the simple illustrations here given; for these the reader is referred to Darwin's work. This subject lias its economical application; the attempts to produce vanilla in the East Indies have failed, the plants, while they grow and flower abundantly, bearing no fruit. It is believed that the insect which fertilizes the flower in Central America is needed to complete the act. The ovary in orchids is inferior (9, fig. 1), and is twisted half a turn in such a manner as to reverse the position of the parts of the flower; thus the lip, which is structurally the superior petal, is by this torsion of the ovary made to appear as the inferior or lower. In ripening, the ovary forms a one-celled, leathery or membranous, cylindrical or ovoid capsule, with innumerable seeds of an appearance which has been likened to fine sawdust. - Orchids are found in nearly all countries except those upon the borders of the frozen zone, and those of excessive dryness.
In northern localities the species are terrestrial, usually inhabiting marshy places or shady woods; in tropical countries many of them are epiphytal, growing upon the branches of trees in dense and humid forests without contact with the earth. In this country there are east of the Mississippi about 70 species of orchidaceoe distributed in 18 genera, and all of these are terrestrial, except two epiphytal species of epi-dendrum found in Florida. Calypso borealis extends in British America as far north as lat. 68°; this is also found in northern Europe, and is the most boreal species known. Our most conspicuous orchids are the cypripedi-ums, already referred to; but some of the smaller flowered ones, such as Arethusa and Calypso, are plants of great beauty, while some species of pogonia are exceedingly grotesque. Our largest genus is habenaria (Lat. habena, a thong or rein, in reference to the shape of the lip in some species); this includes about 20 species, some of which, like H. Integra, are not at all showy.
Orbiculata, the flower of which has been already mentioned, is noticeable for its two large, orbicular leaves, sometimes 8 in. across, which lie flat upon the ground; this is frequently met with in pine and hemlock woods. The white-fringed orchis (77. blephariglottis) and the yellow-fringed (77. ciliaris) are objects of real beauty; and there are three fine lilac or purple-flowered ones to be found in our moist meadows and bogs. Of the genus orchis we have but a single representative, the showy orchis (0. spectabilis), which is found from Kentucky northward, in rich, moist woods; it has two oblong shining leaves, 3 to 5 in. long, from between which rises the flower stalk, about 6 in. high, bearing a few handsome white and pinkish flowers. England has 10 species of orchis. - Though so large a family, the or-chidacem yield but few useful products, the most important commercially being the pods of several species of vanilla. (See Vanilla.) The tubers of some species contain a form of nutritive starch, associated with a peculiar gum; these are collected and dried, and are found in commerce as salep.
Orchids are among the most valued of cultivated flowers, some for their beauty, others for their fragrance, and others for their grotesque forms.
Fig. 1. - Structure of Flower in Orchids (Habenaria orbiculata).
Pollen Mass: a, just detached; 0, after a few seconds.
Fig. 3. - Head of Sphinx with recently attached Pollen Masses.
Fig. 4. - Head of Sphinx with Pollen Masses deflexed.
Fig. 5. - Butterfly Orchis (Oncidium papilio).
Their simulative forms are sometimes wonderful; the flowers of one species are quite like the mouth of a cuttle fish, in others the resemblance to a large spider is equally strong, and in several species the flowers almost exactly imitate various insects; this is notably the case in the butterfly orchis, oncidium papilio, the flowers of which, in size, form, and color, are like a gaudy butterfly. In peristeria the column takes on the form of a dove. (See Holy Spirit Plant.) Among wealthy horticulturists the cultivation of orchids is often a passion, and fine specimens of rare species are purchased at almost incredible prices; the growing of large specimens is slow work. At the sale of the celebrated collection of Mr. Mendel in England in the spring of 1873, single specimens brought as high as £20, £40, and one plant £59 17a., the returns for the whole collection being £4,301. At the few sales which have been held in this country, very food prices have been paid. Some orchids are remarkable for the duration of their flowers, which renders them especially valuable in floral decorations.
The finest collection of these plants in this country (and one of the finest anywhere) is that of Mr. George Such, South Amboy, N. J.
Fig. 6. - Orchis in cultivation (Phalrcnopsis amabilis).