[Illustration: FIG. 146.—ORCHIS MORIO.] [Illustration: FIG. 147.—POLLEN MASSES OF THE ORCHIS.] The plants belonging to this order may be divided into two kinds, those that grow in the earth, and those which require to have their roots suspended in the air; the latter being the beautiful tropical plants called Orchideous Epiphytes. Most of the terrestrial Orchidaceæ are British plants belonging to several genera, the most curious of which are Orchis, Habenaria, Ophrys, Aceras, Nœttia, Epipactis, and Malaxis. Nearly all the British Orchidaceæ have tuberous roots, which remain above ground, a new tuber being formed every year. The leaves are alternate, with an entire margin, without any footstalk, and sheathing the stem at the base. The flowers are produced in a spike, furnished with bracts, and though they are very irregular in their forms, there are certain particulars in which they all agree. Though in reality sessile, they appear to have each a footstalk, but this footstalk is only the long twisted ovary (_c_ in _fig._ 146), which is one-celled and many-seeded, and which serves to support the calyx and corolla of the flower, which are both above it. The calyx consists of three sepals, one of which has the appearance of a hood (_a_), and the others (_b b_) look like wings. The petals are very disproportionate in their size; two are generally very small, and are only seen peeping beneath the hood of the calyx; while the third (_d_), which is called the labellum, or lip, is very large, and hangs down. In the centre of the flower is a singular mass, called the column, composed of the stamens and pistil, grown together (see _a_ in _fig._ 147). In this column there is one perfect anther (_b_), and two imperfect ones (_c c_). The perfect anther consists of a pouch or bag, which, when opened, displays two stalked masses of globular pollen, one of which (_d_) is pulled down to show its appearance, while the other remains in its case at (_e_). The stigma is a sort of cup half full of a glutinous fluid, but it appears entirely shut out from the pollen, which is not only enclosed in its pouch or bag, but is of such a solid waxy nature as to prevent any possibility of its being carried by wind or insects to the stigma. Nature, however, has contrived a means of obviating the difficulty. At the foot of each stalk of the pollen masses, there is a little protuberance, covering a gland, through which the pollen descends to the stigma, and thence to the ovary or germen.