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Pistia Linn.


Description from Flora of China

Apiospermum Klotzsch; Kodda-Pail Adanson.

Herbs, small, free-floating, evergreen, stoloniferous, acaulescent, with spreading feathery roots. Leaves several in a rosette, densely pubescent; petiole very short, almost absent; sheath ligulate, very short, very thin, scarious at base; leaf blade obovate-cuneate to obovate-oblong, somewhat spongy, apex rounded, truncate, or retuse; midrib absent, primary veins subparallel, all arising from base, diverging slightly and running into margin near apex, strongly prominent abaxially, higher order venation reticulate. Inflorescence solitary, very small, much shorter than leaves; peduncle very short, pubescent. Spathe somewhat constricted centrally, pubescent outside, glabrous inside, proximal margins connate with each other and with ovary wall forming tube, free margins between tube and blade folded between stigma and male organs forming a partition between a distal male partial chamber and a proximal female one; limb erect, ovate, expanded, acute-acuminate. Spadix shorter than spathe, mostly adnate to spathe, only apical male zone free; female zone with single gynoecium at base and a thin, green, pouch-shaped flap just below spathe partition; male zone subtended by a thin, marginally lobed, green, annular flap, consisting of a basally naked spadix axis supporting a single whorl of 2-8 flowers, naked axis sometimes extending slightly beyond. Flowers unisexual, naked. Gynoecium obliquely adnate to spadix axis; ovary ovoid, 1-loculed; ovules numerous, orthotropous; placenta broad, apparently parietal, probably morphologically basal; stylar region attenuate, bending inward toward male flowers; stigma disciform-subcapitate, small. Male flower a synandrium consisting of 2 connate stamens; thecae dehiscing by single apical slit. Fruit a thin-walled, utricular, several-seeded, ellipsoid berry, irregularly breaking up and decaying to release seeds. Seed barrel-shaped, ± subtruncate and excavated at apex and base; testa thick, reticulate-alveolate, thicker and with operculum at micropylar end; embryo obovoid to conic; endosperm copious.

One species: widely distributed in tropical and subtropical regions, including China.

(Authors: Li Heng (李恒 Li Hen); Peter C. Boyce)


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