HABIT : seasonally dormant herbs, rhizome short, erect, hypogeal, sometimes branching. LEAVES : several. PETIOLE : sheath rather long, up to at least half as long as petiole. BLADE : lanceolate to broadly ovate, sagittate, hastate or rarely cordate; basal ribs well-developed, primary lateral veins pinnate, sometimes only weakly differentiated, forming submarginal collective vein, 2 or more distinct marginal veins also present, secondary laterals parallel-pinnate, higher order venation parallel-pinnate near midrib, becoming reticulate towards margin. INFLORESCENCE : 1-2 in each floral sympodium. PEDUNCLE : subequal to or shorter than petiole, erect at anthesis, bent downwards in fruit. SPATHE : constricted between tube and blade, tube convolute, externally green to yellow-green, ellipsoid, persistent, blade green to white, erect, widely expanded (P. sagittifolia) or only gaping (P. virginica), later deciduous. SPADIX : cylindric, female zone shorter than male, either contiguous with male zone or with a short zone of sterile flowers in between, male zone with short terminal appendix of sterile flowers. FLOWERS : unisexual, perigone absent. MALE FLOWER : synandrium 4-5-androus, truncate, often slightly excavated centrally, anthers lateral, thecae adjacent, oblong-ellipsoid, dehiscing by apical pore. POLLEN : inaperturate, ellipsoid or spherical, medium-sized (mean 33 µm., range 28-37 µm.), exine spinose (P. virginica) or almost psilate (P. sagittifolia). FEMALE FLOWER : gynoecium closely surrounded by 3-5 free staminodes or some staminodes free and others connate or all connate into truncate-urceolate synandrodium, ovary ovoid, 1-locular, ovules 1-few, hemiorthotropous, funicle short, placenta parietal to basal, style shortly attenuate, narrower than ovary, stigma discoid-hemispheric. BERRY : obconical to irregularly subglobose, green to blackish-purple (P. virginica) or red (P. sagittifolia), 1-3-seeded, with mucilaginous contents. SEED : large, ovoid to subglobose, laterally flattened, embryo large, plumule well-developed with 6-7 leaf primordia, endosperm vestigial or absent.