(orchids), a family of perennial, monocotyledonous, herbaceous plants. They are either terrestrial or epiphytic (in the tropics). Terrestrial orchids are usually rhizomic and often have tuberous, thickened roots. They grow in meadows, swamps, and forests, as well as on mountain slopes.
The leaves are entire, vaginate, or amplexicaul; in saprophytic species, they are reduced to flowerless glumes. Epiphytic orchids grow on the trunks and branches of trees.
They attach themselves to supports by means of aerial roots, which also extract moisture from the air. Many epiphytic orchids have thickened stems, or pseudobulbs, in which water and nutrient matter accumulate. Some epiphytes have delicate and succulent leaves, which sometimes fall to the ground in the dry season; others have coarse, stiff evergreen leaves.