Wolffie boréale

Wolffia brasiliensis Weddell var. borealis Engelmann in C. F. Hegelmaier, Lemnac., 127. 1868

Fronds boat-shaped, 0.7--1.5 mm, 1.3--2 times as long as wide, 0.7--1 times as deep as wide, with point at apex bent upward; papilla absent; upper surface intensely green, with 50--100 stomates; pigment cells present in vegetative tissue (visible in dead fronds as brown dots). 2n = 20, 22, 30, 40.

Flowering (very rare) summer--early fall. Mesotrophic to eutrophic, quiet waters in temperate regions; 0--1400 m; Alta., B.C., Ont., Que.; Calif., Colo., Idaho, Ill., Ind., Iowa, Kans., Ky., Mass., Mich., Minn., Mo., Mont., Nebr., N.H., N.Y., Ohio, Okla., Oreg., Pa., S.Dak., Tenn., Utah, Vt., Wash., Wis.

The name Wolffia punctata has been applied to this species in error.

I know of no specimens of Wolffia borealis from Rhode Island.