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FOC | Family List | FOC Vol. 23 | Araceae

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.

1 Petioles and peduncle pubescent; leaf blade abaxially pilose.   1 C. menglaensis
+ Plants glabrous   (2)
2 (1) Plants gigantic, often exceeding 2 m tall; petioles and abaxial surface of leaves white pruinose; inflorescence arising as a fan of 5-13 inflorescences; spathe limb pure white.   2 C. gigantea
+ Plants small to large (very rarely exceeding 1.5 m tall); petioles and abaxial surface of leaves at most grayish glaucous; inflorescence solitary or in pairs, rarely 4 together and then not in a fan; spathe limb not pure white   (3)
3 (2) Plants large, with tuberous, rhizomatous, or stoloniferous stems; spathes yellow   (4)
+ Plants small, stoloniferous; spathes pale green or somewhat purplish or purplish brown   (5)
4 (3) Leaf blade adaxially matte waxy-glaucous and water-shedding (water sometimes forming "mercury droplets"); spathe limb dull yellow, opening only at base slightly above constriction, remainder staying furled; infructescence declined.   3 C. esculenta
+ Leaf blade adaxially glossy and wettable (water forming an even coating); spathe limb bright yellow, spreading and opening flat; infructescence erect.   4 C. antiquorum
5 (3) Stolons very slender, much branched; leaves frequently with dark patches between primary lateral veins; female and male zones contiguous.   5 C. affinis
+ Stolons robust, little branched; leaves usually concolorous green; female and male zones separated by a zone of synandrodes.   6 C. fallax

Lower Taxa


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