Terrestrial; caudex tuberous and subterranean or growing over the surface of the ground and rooting at the lower nodes, the apical portion erect, stout; sap with white latex; petioles amplexicaule, conspicuously sheathed at the base, subterete above the sheath, moderately spongy; blades moderately thin; sagittate, hastate, trisect or pedatisect; midrib sunken above, prominently raised below; primary lateral. veins of the blades or their segments spreading toward the margins, forming several collective veins; tertiary veins conspicuous. INFLORESCENCES 1-several per axil, much shorter than the leaves; spathe convolute at base, tube usually green, sometimes tinged along the open margin with purple, constricted somewhat above the tube; tube mostly ellipsoid, persistent after anthesis; the blade moderately thin, usually white naviculiform at anthesis, promptly deciduous after anthesis; spadix shorter than the spathe, divided into pistillate and staminate portions; the pistillate portion basal, cylindric, densely many-flowered, slightly tapered toward the apex, green to bright orange; staminate portion clavate, usually several times longer than the pistillate portion, slightly constricted above the sterile portion at the base; sterile staminate portions with irregularly shaped sterile staminate flowers, these usually elongated in the direction of the axis. Flowers unisexual, naked; staminate flowers irregularly 4-6-sided, the stamens 4-6, connate to form an obpyramidal truncate synandrium; anthers with thecae obversely oblong-triangular or oblong, opening at the apex of the connective by a short slit; ovaries oblong, to ovoid, coherent by the thickened annuliform styles, 2-4 celled; ovules several or numerous, anatropous; stigma discoid or hemi-spheric-discoid, 3-or 4 lobate. INFRUCTESCENCES with berries cylindroid, 3-4 celled; seeds many per locule, ovoid, shorter than the funicles, testa sulcate.
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.
Small to gigantic terrestrial, evergreen or seasonally dormant herbs with milky latex, stem tuberous and hypogeal or aerial and erect; leaf blade usually cordate or sagittate to pedatisect, submarginal collective vein present, fine venation reticulate; spathe strongly constricted, tube persistent, blade deciduous after flowering; spadix male and female zones separated by conspicuous zone of sterile flowers, fertile to apex; flowers unisexual, perigone absent; male flower a truncate synandrium. Differs from Chlorospatha in having a subglobose, inflated spathe tube, female zone of spadix free from spathe, styles normally discoid (laterally swollen) and coherent (except Xanthosoma plowmanii ), synandrodes (sterile flowers) between male and female flowers well-developed, ± prismatic.
X. sagittifolium and its many varieties are important subsistence food plants throughout the humid tropics of the world due to their starch- and protein-rich tuberous stems (see chapter 15).