Leaves: stipules convolute; blade 1.1--6 cm ´ 0.2--0.7 mm, apex subulate, lacunae present or absent, 0--2 rows on each side of midrib; veins 1. Inflorescences: peduncles 1--3 per plant, cylindric; spikes cylindric, continuous. Fruits obovoid, sides centrally concave; beak median. Flowering and fruiting summer--fall. Acid waters of lakes and streams; 0--100 m; Que.; Conn., Maine, Mass., N.H., N.H., Vt. Potamogeton pusillus subsp. gemmiparus is an uncommon taxon that superficially resembles subsp. pusillus. It can be separated, however, by its continuous inflorescences, whereas those of subsp. pusillus are interrupted.