Lemna perpusilla Torr.

Fronds 1-4 mm long, 0.8-3.0 mm wide, 1-1 2/3 times as long as wide; on the upper surface often 2-3 papules above the node which are bigger than the ones near the tip; wing of the root sheath 2-3 times as long as wide. INFLORESCENCE: plants often flowering and fruiting. INFRUCTESCENCE: Fruit 0.7-1.0 mm long, 0.5-0.7 mm wide; laterally with a winged margin; wing about 0.05 mm wide; style 0.2-0.4 mm long; seed 0.6-0.8 mm long, 0.4-0.6 mm thick, whitish, with 35-70 indistinct ribs, stays within the fruit wall-after ripening; outer seed coat with 5-7 subepidermal cell layers.