Wolffia 



Lemnaceae 



281 



Map 580 



Lemna minor L 



but more general in the lake area and in the area drained by the Wabash 

 River. 



Throughout continental America except the extreme northern part ; also 

 in Eu., Asia, Africa, and Australia. 



3. Lemna minima Phillipi. Least Duckweed. Map 580. The habitats 

 are similar to those of the other species of the genus. It is known in 

 Indiana only from Allen, Cass, and Sullivan Counties. The only Ohio 

 record is from a pond in Paulding County within three or four miles of 

 Allen County, Indiana. 



Ohio, Ind., Minn., Wyo. to Calif., southw. to Fla., La., and Tex. ; also in 

 Mex., Cent. Amer., into S. A. 



4. Lemna perpusilla Torr. Minute Duckweed. Map 581. Known only 

 in the northern third of the state. The only Ohio record is from Mercer 

 County within six miles of Randolph County, Indiana. 



Mass., N. Y., Ohio, Ind., Wis., Minn, to N. Dak., southw. to Fla., Ark., 

 and Kans. ; also in S. A. 



5. Lemna cyclostasa (Ell.) Chevalier. Pale Duckweed. Map 582. This 

 species is local in the lake area and found in organic debris in completely 

 stagnant water in swamps and ponds. 



Mass., N. Y., Ohio, Ind., 111., Wis., Wyo. to Nev., southw. to Fla., Tex., 

 and Calif. ; also in Jamaica, Mex., Cent. Amer., and S. A. 



796. WOLFFIA Horkel 



Plants globose or nearly so, not punctate, loosely cellular; upper surface convex with 

 usually three conspicuous papules; plants not prominent above the surface of the 



water 1. W. Columbiana. 



Plants more or less flattened above and gibbous beneath, brown-punctate, more com- 

 pactly cellular; plants prominent on the surface of the water. 

 Body of plant rounded-ovate, strongly gibbous, slightly unsymmetrical; dorsal sur- 

 face with a single large conical papule 2. W. papulifera. 



Body of plant more or less oblong with upturned acute tip (peanut-shaped), slightly 

 gibbous, symmetrical; dorsal surface with a prominent papule near the center. 

 3. W. punctata. 



