Arietinum L. C. Beck; Calceolus Miller; Criosanthes Rafinesque; Fissipes Small; Hypodema Reichenbach; Sacodon Rafinesque.

Herbs, with short or long rhizomes and many thickened fibrous roots. Stem erect, elongate or short, clustered or well spaced, often with several sheaths at base. Leaves 1 to several, alternate to opposite, sometimes prostrate on substrate, sheathing and amplexicaul at base; blade adaxially green or sometimes marked with black-purple spots, often elliptic to ovate, rarely cordate or flabellate, with parallel, radiating, or 3-5 prominent veins. Inflorescence terminal, with a solitary flower or rarely many flowers; floral bracts often leaflike, usually smaller than leaves, rarely absent; ovary 1-locular. Flowers usually large and showy. Dorsal sepal erect or hooded over lip; lateral sepals usually united to form a synsepal, but free in Cypripedium plectrochilum. Petals spreading horizontally, at an angle below horizontal, or enfolding sides of lip, sometimes spirally twisted; lip deeply pouched and inflated, subglobose or ellipsoid, with incurved lateral lobes and usually also apical margin, hairy within on bottom. Column short, with 2 lateral fertile stamens, a terminal staminode above, and a stigma below; anthers 2-locular, with very short filaments; pollen powdery or glutinous; staminodes often elliptic to ovate, very rarely ligulate or linear, base stalked or not; stigma ± papillose, inconspicuously 3-lobed. Fruit a capsule.

About 50 species: N temperate zone, mainly in temperate Asia and North America, extending south to the Himalayan regions and Central America; 36 species (25 endemic) in China.

(Authors: Chen Xinqi (陈心启 Chen Sing-chi); Phillip J. Cribb)