Orthrosanthus Sweet
Fl.Australas. pt. 11. (1827)

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Name Status: Current

Scientific Description
J. Gathe, Friday 3 October 2008

Common name. Morning Irises. Family Iridaceae.

Habit and leaf form. Herbs (tufted); evergreen, or deciduous. Perennial. Leaves basal, or basal and cauline (numerous basal, 2–3 cauline). Plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves; rhizomatous. Helophytic to xerophytic. Leaves alternate; 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; 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 present, or 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 aggregated in ‘inflorescences’; in cymes, or in spikes, or in panicles. The terminal inflorescence unit cymose, or racemose. Inflorescences terminal, or axillary; scape erect, terete, 1–3 reduced leaves or not so; inflorescence 2 to many-flowered, compound, branched, with rhipidia, clusters, or solitary flowers; spatheate (2 enclose each inflorescence, cluster or solitary flower, persistent, herbaceous). Flowers pedicellate (almost sessile); bracteate (1 per flower, membranous, herbaceous, 2 subtend each cluster or solitary flower, spathe-like); ebracteolate; small to large; regular; 3 merous; cyclic; tetracyclic. Perigone tube present. Free hypanthium less than 2 mm long. Perianth of ‘tepals’; 6; 2 -whorled; isomerous; petaloid; without spots, or spotted; similar in the two whorls, or different in the two whorls; blue (with distinct midveins). Androecial members definite in number. Androecium 3. Androecial members adnate; all equal; free of one another, or coherent (connate for up to three quarters of their length); when united, 1 - adelphous; 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 dorsifixed, or 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 few; arillate, or non-arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal (from the apex). Fruit 3 celled; few. Seeds endospermic. Endosperm oily. Cotyledons 1 (coleoptile-like). Embryo straight (small). Testa without phytomelan.

Etymology. From the Greek orthros (dawn, early morning) and anthos (flower); common name-morning iris.

Taxonomic Literature

Wheeler, Judy; Marchant, Neville; Lewington, Margaret; Graham, Lorraine (2002). Flora of the south west, Bunbury, Augusta, Denmark. Volume 1, introduction, keys, ferns to monocotyledons. Australian Biological Resources Study. Canberra.

Marchant, N. G.; Wheeler, J. R.; Rye, B. L.; Bennett, E. M.; Lander, N. S.; Macfarlane, T. D.; Western Australian Herbarium (1987). Flora of the Perth region. Part two. Western Australian Herbarium. Perth.

Australia. Bureau of Flora and Fauna (1986). Flora of Australia. Volume 46, Iridaceae to Dioscoreaceae. Australian Govt. Pub. Service. Canberra.