Orchideae

Herbs of various habit, rarely shrubby , of two principal forms: 1, terrestrial , tuberous-rooted herbs ,with annual herbaceous simple stems and solitary or spicate or racemose flowers ; 2, epiphytes with perennial stems or branches variously thickened and forming a pseudobulb, flowering from the top sides or base of the pseudobulb. Perianth superior, irregular , of 6 free or variously combined pieces ; 3 outer (sepals) more or less alike base (mentum) ; 3 inner (petals) dissimilar , the 2 lateral alike, the other (lip) usually very differently shaped . Stamens and style united in a column opposite the lip , anther (except in Cypripedieae)solitary on the front or top or back of the column and free or adnate to it , 2 celled or by subdivisions 4 celled ; top of the column sometimes produced in front (towards the lip) into a beak (rostellum); pollen grains usually cohering in each cell into 1, 2 or 4 pairs of oblong globose or pyriform waxy or powdery masses (pollinia) which are free or attached by pairs or fours to a viscus or gland, or a stalk (caudicle) that terminates in a gland and by which the pollen mass or masses may be removed entire. Ovary inferior , 1 celled (3 –celled in Apostasia), usually linear and twisted ; stigma a viscid surface on the top or concave face of the column, opposite the lip and below the anther (in Cypripedium the anthers are 2 , one on each side of the base of a short style with a discoid stigma). Seeds minute, testa lax enclosing a homogeneous nucleus.-Genera 340, species about 5000, temperate and tropical , rarely arctic.