Family Cannaceae
Cannaceae Juss.Habit and leaf form. Herbs. Perennial; with neither basal nor terminal aggregations of leaves; 0.5–5 m high; rhizomatous. Helophytic, or mesophytic. Leaves medium-sized to large; alternate; spiral; flat, or rolled; more or less petiolate; sheathing. Leaf sheaths with free margins. Leaves simple; epulvinate. Lamina entire; linear, or lanceolate, or oblanceolate; pinnately veined (with parallel-convergent laterals); without cross-venules; attenuate at the base. Lamina margins entire; flat. Vernation convolute. General anatomy. Plants with silica bodies (these internal, in association with the vascular bundles). Accumulated starch other than exclusively ‘pteridophyte type’. Leaf anatomy. Epidermis without silica bodies. Stomata present; paracytic, or tetracytic (or hexacyclic). Guard-cells not ‘grass type’. Lamina without secretory cavities. The mesophyll not containing mucilage cells; containing calcium oxalate crystals. The mesophyll crystals druses, or solitary-prismatic (not raphides). Midrib conspicuous. Minor leaf veins without phloem transfer cells (Canna). Vessels absent. Stem anatomy. Young stems cylindrical (terete). Secretory cavities present; with mucilage. Secondary thickening absent. Xylem without vessels. Root anatomy. Root xylem with vessels and without vessels (mainly simple). Reproductive type, pollination. Plants hermaphrodite. Floral nectaries present. Nectar secretion from the gynoecium (from septal nectaries). Pollination entomophilous; mechanism conspicuously specialized (pollen is shed on the style in the bud, and later insects alighting on the labellum touch first the terminal stigma, then the pollen). Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in spikes, or in panicles (thyrses). The ultimate inflorescence unit cymose. Inflorescences scapiflorous, or not scapiflorous; terminal; spikes or thyrses, usually composed of 2-flowered cincinni; pseudanthial (in that the pairs of homodromous, asymmetric flowers are mirror images of one another). Flowers bracteate (the bracts usually green and fairly inconspicuous, often small); bracteolate (with a bracteole to the left of one flower, and to the right of the other (behind the one or the other of the two lateral sepals), in each flower pair); very irregular; asymmetric (obliquely orientated, with no clearly median organs). The floral irregularity involving the perianth and involving the androecium. Flowers fundamentally 3 merous (but with the androecium modified); partially acyclic. The perianth acyclic (the calyx spiral). Perigone tube absent (in that the sepals are free, the tube being derived from corolla and androecium). Perianth with distinct calyx and corolla, or of ‘tepals’; 6; if considered not resolved into calyx and corolla, more or less petaloid; different in the two whorls (or rather, in the two series:the outer members (sepals) greenish or purplish and subpetaloid, smaller). Calyx 3; polysepalous; persistent. Corolla 3; 1 whorled; gamopetalous (into a tube, along with the stamen and staminodes); unequal but not bilabiate (one member often shorter than the other two). Androecium (2–)4(–5) (the member across the flower from the inner median tepal always lacking). Androecial members adnate (to the tube); markedly unequal; coherent (shortly connate at the base); (theoretically) 2 whorled. Androecium including staminodes. Staminodes (1–)3(–4) (with at least one staminodal member of the inner androecial whorl, wider than the others and sometimes called the ‘labellum’, always being represented); external to the fertile stamens and in the same series as the fertile stamens; petaloid (more conspicuous than the true perianth). Stamens 1 (the median (posterior) member of the inner whorl); reduced in number relative to the adjacent perianth; oppositiperianthial (the single half-anthered stamen being opposite the inner median (posterior) tepal); petaloid (the single fertile stamen bearing only one half-anther, one one edge and often far below the apex). Anthers (or rather, the half-anther) adnate; dehiscing via longitudinal slits; introrse; unilocular; bisporangiate. The endothecial thickenings spiral. Microsporogenesis successive, or simultaneous (?). Anther wall of the ‘monocot’ type. Tapetum amoeboid, or glandular. Pollen shed as single grains. Pollen grains nonaperturate; 2-celled. Gynoecium 3 carpelled; partly petaloid (the style being straight, flat and fleshy-petaloid). Carpels isomerous with the perianth. The pistil 3 celled. Gynoecium syncarpous; eu-syncarpous; inferior. Ovary 3 locular. The ‘odd’ carpel anterior. Gynoecium stylate. Styles 1; apical. Stigmas wet type; papillate; Group III type. Placentation axile. Ovules 20–50 per locule (‘many’); arillate, or non-arillate (depending on interpretation of funicular structures); anatropous; bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells not formed. Synergids pear-shaped. Hypostase present. Endosperm formation cellular, or nuclear (?). Embryogeny asterad. Fruit non-fleshy; dehiscent; a capsule (usually warty). Capsules opening by collapse of the pericarp. Seeds thinly endospermic (the endosperm consisting of a thin, starchy layer). Perisperm present (surrounding the endosperm). Seeds wingless. Seeds with starch. Embryo well differentiated. Cotyledons 1. Embryo straight. Testa operculate; without phytomelan; black (?), or brown. Seedling. Hypocotyl internode present (short). Mesocotyl absent. Seedling collar conspicuous. Cotyledon hyperphyll compact; non-assimilatory. Coleoptile present to absent (there being a somewhat extended cotyledon sheath). Seedling cataphylls absent. First leaf dorsiventral. Primary root persistent. Physiology, biochemistry. Not cyanogenic. Alkaloids absent (3 species). Proanthocyanidins present; cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid absent. Saponins/sapogenins absent. C3. C3 physiology recorded directly in Canna. Anatomy non-C4 type (Canna). Geography, cytology. Sub-tropical and tropical. West Indies and Central America. X = 9. Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Zingiberiflorae; Zingiberales. APG 3 core angiosperms; Superorder Lilianae; commelinid Monocot; Order Zingiberales. Species 55. Genera 1; only genus, Canna. Economic uses, etc. Ornamental hybrids (C. ‘generalis’) are among the most widely grown tropical bedding plants. Illustrations. |
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