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The Orchidaceae

Flowering Plant Families, UH Botany The Orchidaceae are terrestrial, epiphytic, or saprophytic herbs comprising one of the two largest families of flowering plants with about 1,000 genera and 15-20,000 species. The leaves are alternate or seldom opposite or whorled and have a sheathing base and an entire, often fleshy, parallel-veined blade. The flowers are typically zygomorphic and bisexual but sometimes are virtually actinomorphic and rarely are unisexual. The perianth consists of 6 tepals in two similar or dissimilar whorls. The outer whorl of 3 distinct or variously connate tepals is sometimes sepaloid. Two members of the inner whorl of 3 tepals are alike and may be quite similar to the outer tepals. The third tepal of the inner whorl forms a labellum that typically is highly modified in shape and or coloration. The androecium and gynoecium are nearly always adnate into a column or gynostegium. Orchids in subfamily Cypripedioideae have two stamens, one on each side of the column. Orchids in the largest subfamily Orchidoideae have a single terminal stamen and the anthers generally produce one or more waxy masses of pollen called pollinia. The gynoecium consists of a single compound pistil of 3 carpels that together with the androecium comprises the column in most species. The stigma is just proximal to the single terminal stamen in most species. The stigma is two- or three-lobed and the ovary is inferior and almost always has 1 locule with very numerous, up to several million, very tiny parietal ovules. The fruit is mostly capsular.

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