Plant: annual aquatic or terrestrial herb; in water, mostly submerged but usually with a floating rosette of leaves Leaves: polymorphic; submerged leaves linear, 1-15 mm long, 0.3-1.0 mm wide, the margins entire, the apices bifid or emarginate with the single nerve often extending to a callous point, the bases clasping the stem, the leaf base pairs usually adjoining or less often separated by a ridge or wing at the node; floating or terrestrial leaves petioled, 3-nerved, obovate to oblanceolate to spatulate, 1-15 mm long, 1-5 mm wide, the marginsentire, the apices rounded to slightly retuse, the bases as above, the surface covered with minute scales and appearing punctate Inflorescence: with usually 1 staminate and 1 pistillate flower in each axil Flowers: subtended by a pair of whitish inflated bracteoles, 0.5-1.5 mm long, usually deciduous in fruit; styles 1-6 mm long, erect or spreading, often persistent Fruit: nutlets, brown at maturity, sessile, 0.5-1.4 mm long, 0.6-1.2 mm wide, usually 0.2 mm longer than wide, obovate, the margins flattened, winged (conspicuous on mature material), widest at the apex, often inconspicuous on the sides and bases, the groove between carpels evident between the wings, the surface pits appearing more or less aligned in vertical rows Misc: Lakes, ponds and slow-moving streams; 2050-2850 m (6700-9400 ft); May-Aug (fr. Aug-Oct) REFERENCES: Ricketson, Jon. 1995. Callitrichaceae. J. Ariz. – Nev. Acad. Sci. 29(l): 15.