Prostrate, floating herb or "subshrub," the submerged stems spongy-inflated with a pithy outer surface, bearing nodular roots, the above-water stems glabrous, flexuous, not lenticellate. Leaves moderate, 2-ranked, bipinnate, the pinnae mostly 3 pairs opposite on the rachis, the leaflets usually about 15 pairs per pinna; petioles mostly 2-3 cm. long, glabrous, somewhat flattened above, eglandular or with an apical callus just below insertion of the basal pair of pinnae; rachis similar to and approximating the petiole; pinnae usually 2-4 cm. long, the pairs moderately re-mote from one another, glabrous; leaflets linear or linear-spatulate, 3-12 mm. long and 1-3 mm. wide, rounded or obtuse and often briefly mucronulate apically, obliquely rounded or subtruncate basally, glabrous, the venation obscure; stipules inequilaterally ovate-lanceolate, generally about 5 mm. long, glabrous, not striate. Inflorescence of axillary, pedunculate heads or very short spikes; peduncles elongate, as much as 15 cm. long, glabrous, usually bearing near or below the middle 2 rather small bracts; heads obovoid in bud, dense, bearing staminate or infertile flowers basally and perfect flowers apically. Flowers sessile, bi-(tri?)-morphic, reportedly whitish fading yellow; calyx of perfect flowers, cupulate-funnelform, about 2 mm. long (smaller in basal flowers), glabrous, 5-lobed; corolla of 5 linear-spatulate petals, about 4 mm. long, glabrous; stamens of perfect flowers about 10, 7-8 mm. long; staminodia of basal flowers normally 10, petaloid, as much as 15 mm. long, glabrous; ovary glabrous; style exceeding the stamens; stigma expanded, truncate. Legume oblong, 10-25 mm. long and about 8 mm. wide, flat, somewhat curved, stipitate, briefly beaked, glabrous, few-seeded, the seeds transverse.
Home