Petterson, B. (1995) Orchidaceae in Flora of Somalia 4: 70-76
Plants usually epiphytic to terrestrial perennial herbs, sometimes shrubs, sometimes saprophytic; perennating organs in terrestrial species rhizomes or pseudobulbs, in epiphytes pseudobulbs, rhizomes, or entire plants. Inflorescences spikes, racemes, or panicles. Flowers bisexual, bilaterally symmetric, usually twisted through 180 degrees (resupinate). Tepals 6, arrranged in 2 whorls, both whorls similar, or the outer calyx-like and the inner corolla-like; median petals (lip)almost always different from the lateral petals, entire or varioulsy lobed, laciniate, or fimbriate, often brightly coloured, spotted, or otherwise ornamental, often bearing crests of cushions of hairs, often extending backwards and forming a spur, rarely forming 2 spurs, spurs often with nectar in their tips; stamens usually 1, rarely 2, more of less united with the styles to form the column; pollen usually aggregated into 2 (sometimes, 4, 6, or 8) pollinia per flower; pollinia mealy, waxy, or horny, often divided into a number of smaller portions; ovaries inferior, 1-celled. Fruits capsules opening by lateral slits; seeds minute and very numerous, requiring formation of a mycotrophic partner for germination.
The Orchidaceae family includes about 725 genera and 20,000 species, Most species grow in areas with high rainfall. Many epiphytes and some terrestrial species are succulent (the pseudobulbs being thick or terete leaves) or other adaptations (such as leathery leaves and velamen) to cope with dry periods.