5. Wolffia columbiana H. Karsten, Botanische Untersuchungen. [Landwirthschaftliche Lehranstalt. Physiologisches Laboratorium] Berlin. 1: 103, figs. 2g, 3g. 1865.
Wolffie de Colombie
Fronds nearly globular, 0.5--1.4 mm (x 0.4--1.2 mm), 1--1.3 times as long as wide, 1--1.3 times as deep as wide, rounded at apex, papilla absent; upper surface transparently green, with 1--10(--30) stomates; pigment cells absent in vegetative tissue. 2n = 30 (H, U), 40 (U), 42 (D), 500 (U), 70 (70), 80 (U).
Flowering (very rare) summer--early fall. Mesotrophic to eutrophic, quiet waters in temperate to subtropical regions; 0--1100 m; Alta., Man., Ont., Que., Sask.; Ala., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., S.C., S.Dak., Tenn., Tex., Vt., Va., W.Va., Wis.; Mexico; West Indies (Curaçao); Central America; South America.
I know of no specimens of Wolffia columbiana from Rhode Island.
OTHER REFERENCES Dore, W. G. 1957. Wolffia in Canada. Can. Field-Naturalist 71: 10--16. Brooks, J. S. 1940. The Cytology and Morphology of the Lemnaceae. Ph.D. thesis. Cornell University. Landolt, E. and Urbanska-Worytkiewicz K. 1980. List of the studied Lemnaceae samples: origin and chromosome numbers. Veröff. Geobot. Inst. Rübel Zürich 70: 205--247.
