Iridaceae Juss.

Scientific Description

Common name. Iris Family.

Habit and leaf form. Herbs, or shrubs (rarely); evergreen, or deciduous. Perennial; plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves; rhizomatous, or cormous, or bulbaceous (a few). Helophytic to xerophytic. Leaves alternate; usually distichous; ‘herbaceous’, or leathery; sessile, or petiolate; sheathing. Leaf sheaths with free margins. Leaves foetid (sometimes), or without marked odour; edgewise to the stem (usually), or with ‘normal’ orientation; simple; epulvinate. Leaf blades entire; flat, or solid; linear, or lanceolate; parallel-veined; without cross-venules. Leaves eligulate. Leaf blade margins entire. Leaves with a persistent basal meristem, and basipetal development. Stem anatomy. Secondary thickening absent, or anomalous (in Klattia, Nivenia, Witsenia); when present, from a single cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present (mostly), or absent. Nectar secretion from the perianth (mostly, from nectaries at the tepal bases), or from the gynoecium (septal nectaries in Ixioideae). Entomophilous, or ornithophilous, or anemophilous (rarely).

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; in panicles, in cymes, in spikes, in umbels, and in corymbs. The terminal inflorescence unit (when more than one-flowered) cymose, or racemose. Inflorescences nearly always scapiflorous (but some with the inflorescence reduced to a single, almost sessile flower); terminal; panicles, thyrses, cymes, spikes — often hard to interpret; spatheate (via one or two expanded, bladeless sheaths). Flowers bracteate; small to large; regular to very irregular; when irregular, zygomorphic; 3 merous; cyclic; tetracyclic (usually). Perigone tube present (long or short). Perianth of ‘tepals’; 6; 2 -whorled; isomerous; petaloid; without spots, or spotted (commonly); similar in the two whorls, or different in the two whorls (the inner sometimes much smaller); white, or yellow, or red, or purple, or violet, or blue (or blue-green). Androecium (2–)3. Androecial members free of the perianth, or adnate (to the perianth tube); free of one another, or coherent (the filaments often united into a basal tube); when united, 1 - adelphous; 1 -whorled (representing the outer whorl). Androecium exclusively of fertile stamens. Stamens (2–)3; reduced in number relative to the adjacent perianth to isomerous with the perianth; alterniperianthial (opposite the outer perianth lobes). Anthers basifixed; dehiscing via longitudinal slits; extrorse. Gynoecium 3 carpelled. The pistil 3 celled, or 1 celled (very rarely). Gynoecium partly petaloid (commonly), or non-petaloid; syncarpous; synstylovarious, or eu-syncarpous; inferior (nearly always), or superior (very rarely —Isophysis). Ovary unilocular, or plurilocular; 3 locular, or 1 locular (Isophysis). The ‘odd’ carpel anterior. Styles 1 (3-lobed, the lobes sometimes subdivided or often expanded and petaloid); apical. Stigmas dry type; papillate; Group II type. Placentation when unilocular (i.e. very rarely), parietal; nearly always axile. Ovules (1–)2–50 per locule (i.e. to ‘many’); arillate, or non-arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Seeds endospermic. Endosperm oily. Seeds usually without starch. Cotyledons 1 (coleoptile-like). Embryo achlorophyllous (3/5), or chlorophyllous (Tritonia crocosmifolia); straight (small). Testa without phytomelan. Seedling. Hypocotyl internode present, or absent. Seedling collar not conspicuous. Cotyledon hyperphyll elongated, or compact; assimilatory, or non-assimilatory; more or less circular in t.s. Coleoptile present, or absent. Seedling cataphylls present, or absent. First leaf ensiform. Primary root ephemeral.

Physiology, biochemistry. Photosynthetic pathway: C₃.

Geography, cytology, number of species. Holarctic, Paleotropical, Neotropical, Cape, and Australian. World distribution: almost cosmopolitan, but lacking from frigid zones and northern Eurasia. X = 3–19 (or more). 1800 species.

Economic uses, etc. Numerous ornamentals, plus orris root (from Iris rhizomes) and saffron dye (from Crocus stigmas).