Cactaceae

Abstract

Succulent perennials of diverse habit, trees, shrubs, climbers, epiphytes or geophytes; roots fibrous or tuberous; stems columnar, terete, globular, tubercled, ribbed, winged or flattened, often segmented, mostly leafless and variously spiny; leaves, where present, spirally arranged, simple, entire, exstipulate, but usually rudimentary or vestigial; axillary buds developing a persistent cushion-like indumentum of multicellular trichomes (areole), and usually leaves transformed into spines. Flowers solitary or rarely clustered, usually sessile at the areoles, rarely pedicellate in paniculate or cymose inflorescences (Pereskia) or terminal (e.g. Pterocactus), zoophilous, often conspicuous, nearly always bisexual, usually actinomorphic; receptacle enclosing, and more or less produced beyond the zone around the ovary (“pericarpel”) and between ovary and perianth (epigynous hypanthium; “tube”), naked or invested with bractlike scales and aréoles, areolar trichomes, hairs and/or spines, the upper scales often intergrading with the outer tepals; tepals usually numerous in a graded series; stamens often very numerous; anthers 2-locullar, tetrasporangiate, dehiscing longitudinally; ovary inferior (except some Pereskia spp.), unilocular, 3–20-carpellate, placentation usually hypanthial, rarely basal-laminal, ovules numerous; style usually long; stigma 3–20-lobed.