by Nathaniel Lord Britton & Addison Brown

“ Amphibious or uliginous, usually emersed when mature; leaves 10-30, green, rather rigid, 4'-8' long, quadrangular, bearing numerous stomata; peripheral bast-bundles wanting; ligule rather short, triangular; sporange mostly oblong, distinctly spotted with groups of brown cells, one-fourth to three-fourths covered with the velum; macrospores 450-756 μ in diameter, marked with distinct or anastomosing jagged crests or somewhat reticulate on the lower side; microspores 28-32 μ long, more or less tuberculate. ”

“ Leaves 10-20, 21⁄2′–3′ long, blunt at the apex, without stomata; sporange spotted with dark cells, covered one-third to two-thirds by the velum; macrospores 486-720 μ in diameter, polished, covered with bold vermiform, subconfluent and somewhat reticulated ridges, becoming naked near the equator; microspores 31-44 μ in diameter, distinctly verrucose.
Nova Scotia to Quebec and Maine; usually growing in ponds and lakes. ”

“ Aquatic or marsh plants rooting in the mud, with a short buried 2-lobed or 3-lobed trunk (stem) sending out abundant roots and sending up a compact tuft of rush-like leaves. Sporanges sessile in the axils of the leaves, some containing megaspores (megasporanges) , others microspores (microsporanges) ”