Xanthosoma Schott

Latex milky. HABIT : small to gigantic, sometimes arborescent, evergreen or seasonally dormant herbs, stem either a thick, subcylindric, hypogeal tuber often producing smaller tubers on stoloniferous side branches or often with a distal, epigeal, massive, arborescent upper part, or an entirely hypogeal subglobose tuber, bearing many very small tubercles in some spp. (X. pubescens, X. viviparum), tuber sometimes yellow within. LEAVES : several, rarely pubescent. PETIOLE : sheath usually rather long. BLADE : cordate, sagittate, hastate, trifid, trisect, pedatifid or pedatisect, rarely linear-lanceolate to ovate with emarginate base, rarely peltate; basal ribs well-developed, often denuded proximally, primary lateral veins pinnate, forming submarginal collective vein, 1 or more distinct marginal veins also present, secondary and tertiary laterals arising from the primaries at a wide angle, forming interprimary collective vein, higher order venation reticulate. INFLORESCENCE : 1 to many in each floral sympodium, always appearing with leaves. PEDUNCLE : usually rather short, rarely long. SPATHE : strongly constricted, tube with convolute margins, ovoid to ellipsoid, usually ventricose, rather thick-walled in large species, persistent, blade boat-shaped-oblong to -oblong-lanceolate, gaping and erect or sometimes reflexed at anthesis, marcescent after anthesis and then deciduous. SPADIX : shorter than spathe, densely flowered, female zone cylindric-conoid, often obliquely inserted onto peduncle, separated from male zone by longer, conoid to attenuate, basally thicker zone of sterile male flowers, male zone cylindric-conoid, longer than female zone, usually fertile to apex, rarely with a few sterile flowers at extreme apex. FLOWERS : unisexual, perigone absent. MALE FLOWER : 4-6-androus, connate into a truncate-obpyramidal, subpentagonal or hexagonal synandrium, anthers lateral, nearly reaching base of synandrium, common connective thick, thecae obversely oblong or tapering basally, dehiscing by subapical pore or short slit. POLLEN : extruded in strands, shed in tetrads, inaperturate, ellipsoid to subspherical, medium-sized (mean 42 µm., range 35-49 µm., tetrads :- mean 76 µm., range 62-97 µm.), exine minutely punctate- or fossulate-verruculate. STERILE MALE FLOWER : composed of obpyramidal truncate, laterally compressed synandrodes, lowermost larger, uppermost narrower and more elongated (in sense of spadix axis). FEMALE FLOWER : ovary ovoid, 2-4-locular, more rarely 1-locular, ovules (12-)20 to very numerous, anatropous or hemianatropous, funicles rather long, placentae usually pseudoaxile, or sometimes parietal or axile basally, style broader than ovary, usually discoid-thickened coherent to weakly connate with those of neighbouring flowers, rarely free and swollen (X. plowmanii), stigma subhemispheric or 2-4-lobed, yellow, narrower than style. BERRY : cylindric, somewhat furrowed apically, whitish to orange, many-seeded. SEED : ovoid, testa costate, embryo axile, subequal to endosperm, endosperm copious.