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(Last Modified On 10/25/2012)
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(Last Modified On 10/25/2012)
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Genus
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XANTHOSOMA Schott
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PlaceOfPublication
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Melet. 19. 1832.
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Description
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Plants usually large and coarse, terrestrial, arising from a hypogean tuber or from a more or less elongate, hypogean or epigean caudex; petioles long, thick, sub- terete, vaginate below; blades sagittate, hastate, or trisect or pedatisect, the primary lateral nerves of the blades or their segments united to form a more or less distinct collective nerve; peduncles solitary or aggregate, mostly short; tube of the spathe ovoid or oblong, convolute, persistent, constricted at its apex, the limb oblong-cymbiform or oblong-lanceolate; spadix shorter than the spathe, the pistillate portion cylindric, densely many-flowered, narrowed upward, the sterile staminate part longer than the pistillate, narrowed above, the fertile staminate portion thick- cylindric, slightly narrowed upward, twice as long as the pistillate portion or longer; flowers unisexual, naked; stamens 4-6, connate to form a truncate- obpyramidal, 5- or 6-angulate synandrium truncate at its apex; anther cells obversely oblong-triangular or oblong, opening below the apex of the connective by a short slit; ovaries ovoid, coherent by the thickened, annuliform styles, 2- to 4-celled; ovules several or numerous, anatropous; stigma discoid or hemispheric- discoid, 3- or 4-lobate; berries cylindroid, crowned by the impressed stigma, 3- or 4-celled, the cells many-seeded; seeds ovoid, shorter than the funicles, the testa sulcate.
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Distribution
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The genus includes about 40 species, all American. Seven have been reported from Central America.
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Key
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a. Leaves pedatisect - -- 1. X. HELLEBORIFOLIUM aa. Leaves entire. b. Leaves glabrous -. - .. . 2. X. VIOLACEUM bb. Leaves pubescent. c. Basal lobes of the leaf blade rounded, directed downward, sepa- rated by a relatively narrow sinus -..- 3. X. PILOSUM cc. Basal lobes of the leaf blade triangular, directed outward, sepa- rated by a very broad and open sinus - 4. X. MEXICANUM
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