A very large family, most abundant in the tropics; curious plants, with oddly beautiful flowers. Perhaps because they are also rather rare they seem to have a peculiar fascination for the public; in fact almost any strangely-shaped flower is apt to be dubbed an orchid by the passer-by. They are perennial herbs, with various kinds of roots, some of them parasitic, usually with alternate, toothless leaves, the lower ones sheathing the stem. In some kinds the leaves have dwindled to scales. The flowers are perfect, irregular, with six divisions; the three sepals are alike and colored like petals; two of the three petals are alike, but the central one differs in size and shape and is called the lip. This is conspicuously colored, often spurred, and contains nectar for the attraction of " long-tongued" insects, on which these plants depend mostly for cross-pollination. The mechanism for this purpose is curious and interesting. The stigma is usually a broad sticky surface and its style is united with the filaments and forms, in front of the lip, a column which is usually capped by a single two-celled anther, containing two clusters of pollen, one in each cell. Each cluster consists of a few waxy grains, held together by cobweb-like threads, which run together and terminate in a sticky disk. These disks adhere to the insects, which push in to get the nectar, and are transported to the gummy stigma of another flower. The inferior ovary develops into a three-valved capsule, containing numerous minute seeds. Orchis is the ancient Greek name.

There is only one kind of Cephalanthera in North America; with creeping rootstocks; flowers in terminal spikes, with bracts; sepals and petals nearly equal; petals somewhat united and hooded; lip more or less pouched.