24. Colocasia Schott in Schott & Endlicher, Melet. Bot. 18. 1832.
芋属 yu shu
Authors: Heng Li & Peter C. Boyce
Leucocasia Schott.
Herbs, seasonally dormant or evergreen, small, medium sized, or gigantic, latex-bearing. Stem either a hypogeal, subglobose or subcylindric tuber or mostly epigeal, massive. Leaves several, rosulate in acaulescent plants, forming a terminal crown in arborescent species. Petiole glabrous, sometimes strikingly glaucous, rarely pubescent, sheath rather long; leaf blade peltate, ovate-cordate to sagittate-cordate, abaxially glabrous, glaucous, pruinose, rarely pilose; posterior lobes rounded, shortly to almost entirely connate; basal ribs well developed, primary lateral veins pinnate, forming submarginal collective vein, 1 or 2 marginal veins also present, secondary and tertiary laterals arising from primaries at a wide angle, then arching strongly toward leaf margin and forming inconspicuous interprimary collective veins, higher order venation reticulate. Inflorescences 1 to many per each floral sympodium, appearing with leaves; peduncle mostly shorter than petioles. Spathe constricted between tube and limb, sometimes with a second weaker constriction above male zone of spadix; tube persistent, enlarging in fruit and then splitting open irregularly from apex, with convolute margins, usually much shorter than limb, ovoid or oblong; limb either remaining erect, and ± furled, or opening and then reflexed at anthesis, later deciduous, white or yellow, very narrowly lanceolate to oblong or boat-shaped. Spadix sessile, shorter than spathe; female zone short, separated from male by narrower zone of sterile male flowers or contiguous with male zone; male zone cylindric to fusiform; terminal appendix erect, ± smooth, narrowly conic to fusiform or subulate, sometimes reduced to a small, mucronate stub, or absent. Flowers unisexual, naked. Ovary ovoid or oblong, 1-loculed; ovules many, hemiorthotropous; funicles relatively long; placentae 2-5, parietal; stylar region short, narrowed or not, sometimes ± absent; stigma disciform-capitate or weakly lobed. Interpistillar staminodes present in some species, these weakly clavate, equaling associated pistil; interfloral synandrodes (where present) depressed obpyramidal, laterally compressed, truncate. Male flowers 3-6-androus; stamens connate into ± truncate synandrium; thecae lateral, oblong-linear, dehiscing by apical pore. Infructescence erect or declined by flexing of peduncle. Fruit a greenish to whitish or dull orange, obconic or oblong, strongly fruit-smelling berry, many seeded; stigma remnants persistent. Seed tiny, ovoid to ellipsoid; testa thickish, costate; embryo axile, cylindric; endosperm copious.
About 20 species: tropical and subtropical Asia; six species in China.
