Habit and leaf form. Large, erect herbs (from 75-700cm tall). Perennial; with a basal aggregation of leaves, or with neither basal nor terminal aggregations of leaves; cormous. Leaves alternate; distichous; long petiolate; sheathing. Leaf sheaths tubular. Leaves simple. Lamina entire; elliptic or oblong; pinnately veined (with a prominent midrib, from which diverge obliquely the numerous, parallel secondary veins, which arch and merge to form a marginal vein). Leaves eligulate. Lamina margins entire. Vernation convolute.
General anatomy. Plants with `crystal sand', or without `crystal sand'. Plants with silica bodies (rectangular, in associaton with the vascular bundles).
Leaf anatomy. Epidermis without silica bodies. Stomata present; paracytic, or tetracytic.
The mesophyll containing mucilage cells (with raphides); containing calcium oxalate crystals. The mesophyll crystals raphides (and/or crystal sand). Minor leaf veins without phloem transfer cells. Vessels absent.
Stem anatomy. Secondary thickening absent. Xylem without vessels.
Root anatomy. Root xylem with vessels. Vessel end-walls scalariform.
Reproductive type, pollination. Hermaphrodite. Floral nectaries present. Nectar secretion from the gynoecium (via septal nectaries). Ornithophilous.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in `inflorescences'; in panicles. The terminal inflorescence unit cymose (monochasial). Inflorescences scapiflorous, or not scapiflorous; borne on an erect peduncle, consisting of a large, flattened erect or drooping thyrse, often with a conspicuously geniculate axis, each lateral branch subtended by a stiff, usually boat shaped, sometimes quite large and often showy (green, red, orange) bract, the lateral branches consisting of dense monochasial cymes which may be almost concealed in the bract axils; spatheate. Flowers bracteate (the floral bracts smaller and thinner than the cincinnal bracts); very irregular; strongly zygomorphic (the symmetry inverted relative to Costaceae, Musaceae, Strelitziaceae and Zingiberaceae, the the median tepal of the outer whorl being posterior, adaxial). The floral asymmetry involving the perianth and involving the androecium. Flowers 3 merous; cyclic. Perigone tube present to absent (the five joined tepals plus the one one more or less free tepal forming a tube, which can widen without bursting when visited by relatively broad-beaked birds).
Perianth of `tepals'; 6; joined (the median member of the outer series more or less free from the rest, which are fused to form a five-dentate or five-lobed, boat shaped upper lip); 2 whorled; isomerous; petaloid; similar in the two whorls to different in the two whorls.
Androecium 6. Androecial members free of the perianth; free of one another. Androecium including staminodes. Staminodes 1 (closing the slit in the perianth tube); petaloid (somewhat), or non-petaloid (then subulate). Stamens 5; reduced in number relative to the adjacent perianth. Anthers basifixed; tetrasporangiate. Microsporogenesis successive. Pollen grains nonaperturate.
Gynoecium 3. Carpels isomerous with the perianth. Gynoecium syncarpous; synstylovarious to eu-syncarpous; inferior. Ovary 3 locular. Gynoecium stylate. Styles 1 (often somewhat curved and slightly clavate); apical. Stigmas 1, or 3; wet type; papillate. Placentation basal to axile. Ovules 1 per locule; non-arillate; anatropous; bitegmic; crassinucellate. Embryo-sac development Polygonum-type. Endosperm formation nuclear.
Fruit fleshy; a schizocarp; comprising mericarps, or comprising drupelets; 3 seeded. Seeds copiously endospermic. Perisperm present. Seeds triangular. Embryo weakly differentiated (when the seed first matures). Cotyledons 1. Embryo straight. Testa operculate (at the micropylar end); often blue.
Physiology, biochemistry. Not cyanogenic. Proanthocyanidins present.
Geography, cytology. Neotropical. Tropical. Tropical America. X = 12.
Taxonomy. Subclass Monocotyledonae. Superorder Zingiberiflorae; Zingiberales. Species 80. Genera 1; only genus, Heliconia.
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