Fronds boat-shaped, 0.5–1.6 mm, 1–1.5 times as long as wide, 0.3–0.7 times as deep as wide, rounded at apex, papilla usually prominent in center of upper surface (tent-shaped); upper surface intensely green, with 50–100 stomates; pigment cells present in vegetative tissue (visible in dead fronds as brown dots). 2n = 20, 40, 42, 50, 60, 80.
Phenology: Flowering (rare) late spring–early fall.
Habitat: Mesotrophic to eutrophic, quiet waters in temperate to subtropical regions
Elevation: 0–1000 m
Ala., Ark., Calif., Conn., Del., D.C., Fla., Ga., Ill., Ind., Kans., Ky., La., Md., Mass., Mich., Miss., Mo., N.J., N.Y., N.C., Ohio, Okla., Oreg., Pa., S.C., Tenn., Tex., Va., Wash., W.Va., Wis., Mexico, West Indies, Central America, South America.
I know of no specimens of Wolffia brasiliensis from Rhode Island.