Common name. Irises. Family Iridaceae.
Habit and leaf form. Herbs; evergreen, or deciduous. Perennial. Leaves basal and cauline (mostly basal). Plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves; rhizomatous (3–5 cm diameter, fleshy, at the soil surface). Helophytic to xerophytic. Leaves alternate (fan-shaped clusters); distichous; ‘herbaceous’, or leathery; sessile; sheathing. Leaf sheaths with free margins. Leaves foetid, or without marked odour; edgewise to the stem, or with ‘normal’ orientation; simple; epulvinate. Leaf blades entire; flat, or solid; linear, or lanceolate; linear (to ensiform); parallel-veined; without cross-venules; open or closed sheaths. Leaves eligulate; without stipules. Leaf blade margins entire. Leaves with a persistent basal meristem, and basipetal development. Leaf anatomy. Hairs absent. Extra-floral nectaries absent. Stem anatomy. Secondary thickening absent.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present, or absent. Nectar secretion from the perianth (from nectaries at the tepal bases). Entomophilous, or ornithophilous, or anemophilous.
Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; in cymes. The terminal inflorescence unit cymose, or racemose. Inflorescences terminal; scape to 120 cm, 1 or 2 branched; inflorescence with condensed rhipidia of 2–5 flowers; spatheate (2, opposed, persistent, ensheath each ripidium, herbaceous, ovate with a scarious apex). Flowers pedicellate (shortly); bracteate; ebracteolate; small to large; regular; 3 merous; cyclic; tetracyclic. Perigone tube present. Perianth of ‘tepals’; 6; 2 -whorled; isomerous; petaloid; without spots, or spotted; similar in the two whorls, or different in the two whorls; white (usually), or yellow, or violet, or blue (or multicoloured). Androecial members definite in number. Androecium 3. Androecial members adnate; all equal; free of one another; 1 -whorled (representing the outer whorl). Androecium exclusively of fertile stamens. Stamens 3; all more or less similar in shape; reduced in number relative to the adjacent perianth to isomerous with the perianth; on the perianth tube opposite the outer segments; alterniperianthial (opposite the outer perianth lobes). Anthers basifixed; dehiscing via longitudinal slits; extrorse. Gynoecium 3 carpelled. The pistil 3 celled. Gynoecium partly petaloid, or non-petaloid; syncarpous; synstylovarious; inferior. Ovary plurilocular; 3 locular. The ‘odd’ carpel anterior. Gynoecium stylate. Styles 1; apical. Stigmas 3. Placentation axile. Ovules (1–)2–50 per locule; arillate, or non-arillate; anatropous.
Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal (from the apex). Fruit 3 celled. Seeds endospermic. Endosperm oily. Cotyledons 1 (coleoptile-like). Embryo straight (small). Testa without phytomelan.
Etymology. From the Greek for "rainbow", in reference to the diverse colours of the flowers.