Iris Family

Peter Goldblatt

Iris brevicaulis

Herbs, perennial, rarely annual [or shrubs with woody caudex], evergreen or seasonal, sometimes cespitose; rootstock a rhizome, bulb, or corm. Flowering stems aerial (or subterranean in Romulea), simple or branched, terete or variously compressed, angled or winged. Leaves basal and cauline, distichous; proximal 2–3 sometimes membranous, not reaching much above ground; others with open or closed sheaths, usually unifacial [bifacial or terete], oriented edgewise to the stem; blade parallel-veined, plane or pleated, channeled. Inflorescences umbellate, monochasial cymes (rhipidia), spikes, or solitary flowers; rhipidia enclosed in 2, opposed, usually large, leafy to dry bracts (spathes); flowers except for the first subtended by 1 floral bract; spike flowers each subtended by 2, opposed bracts. Flowers usually pedicellate [± sessile]; per-ianth actinomorphic or zygomorphic, petaloid, with 2 equal or unequal whorls of 3 tepals each [1 whorl of 6]; tepals usually large, showy, distinct or connate in tube; stamens 3 [2], inserted at base of outer tepals or in tube, symmetrically arranged or unilateral, arcuate [declinate]; filaments distinct or partly to completely connate, sometimes weak, unable to support anthers; anthers with 2 pollen sacs, extrorse, occasionally latrorse, usually dehiscing longitudinally [rarely apically]; ovary inferior [superior in Tasmanian Isophysis], 3-locular [1-locular]; placentation axile [parietal]; ovules 2–few, anatropous; style single, filiform at least proximally, usually 3-branched or 3-lobed, branches either filiform, distally expanded, sometimes each divided in distal 1/2, stigmatic toward apices, or branches thickened, or flattened, petaloid, stigmas then abaxial below apices. Fruits capsular, loculicidal, rarely indehiscent, firm to cartilaginous, occasionally woody. Seeds globose to angular (prismatic) or discoid, sometimes broadly winged; seed coat usually dry (rarely fleshy); endosperm hard, with reserves of hemicellulose, oil, and protein; embryo small.

Genera ca. 65, species ca. 1810 (16 genera, 92 species; 9 genera, 19 species introduced, and various hybrid complexes in the flora): nearly worldwide but rare in tropical lowlands, best represented in southern Africa.

Iridaceae are currently divided into four subfamilies (P. Goldblatt 1990, 1991). Subfamily Isophysidoideae Takhtajan is monotypic, comprising the Tasmanian Isophysis T. Moore with a superior ovary. Only subfamily Iridoideae is native in North America. The remaining Nivenioideae Schulze ex Goldblatt and Ixioideae Klatt are centered in Africa south of the Sahara. Iridaceae are of considerable economic importance in ornamental horticulture and the cut-flower industry, especially Iris, Gladiolus, and Freesia. Several other genera (e.g., Crocus, Dietes, Sparaxis, Tritonia, Watsonia) are cultivated in gardens in both tropical and temperate areas. Moraea and Homeria are poisonous and pose significant problems in cattle- and sheep-raising areas, notably in southern Africa.

In addition to the several genera and species escaped from cultivation and dealt with in detail below, the following are widely grown in areas of mild winter and may persist in and near abandoned gardens, sometimes reproducing successfully: Dietes Salisbury [D. iridioides (Linnaeus) Salisbury ex Klatt, D. grandiflora N. E. Brown]; Ixia Linnaeus (I. maculata Linnaeus, I. polystachya Linnaeus); Crocus cultivars and even some wild species.

SELECTED REFERENCES

Arber, A. 1921. The leaf structure of the Iridaceae. Ann. Bot. (Oxford) 35: 301–336. Goldblatt, P. 1975. Revision of the bulbous Iridaceae of North America. Brittonia 27: 373–385. Goldblatt, P. 1990. Phylogeny and classification of Iridaceae. Ann. Missouri Bot. Gard. 77: 607–627. Goldblatt, P. 1991. An overview of the systematics, phylogeny and biology of the southern African Iridaceae. Contr. Bolus Herb. 13: 1–74. Reeves, G. et al. 2001. Molecular systematics of Iridaceae: Evidence from four plastid DNA regions. Amer. J. Bot. 88: 2074–2087.