SPECIES OF DESMIDS. loy 



jj. Surface granules emarginate or divided; semi-cells broadly elliptical, 



asperum, 127 



jj. not emarginate; semi-cells elliptic, truncata, 128 



jj. " not emarginate; semi-cells subsemiorbicular, 



angles truncate muricatum, 127 



jj. Surface scabrous, semi-cells elliptic scabrum, 130 



jj. Surface tuberculate; sides at base convex, spinous; a central, 

 spherical, spinous projection conspicuous ... bullosum* 

 jj. Surface tuberculate; sides at base concave; no central protuber- 

 ance tuber culatum* 



jj. " " . " not concave, pseudvcrenatum** 



kk. End view sides concave (//). 



kk. sides nearly straight, very slightly convex (nri). 



kk. sides convex; semi-cells subsemiorbicular, 



muricatum, 127 



//. Semi-cells twisted; 2-3 times longer than wide, elliptic or oblong, 



alternant, 128 



//. Semi-cells not twisted (mm). 

 mm. Front view ends concave; end view angles rounded, 



striolatum, 126 



mm. end view angles acute, Pringlei, 132 



mm. Front view ends convex; end view angles crenate, sides smooth, 



crenatum, 126 

 mm. " " end view angles not crenate, somewhat 



truncate . . '. dilatatum, 128 



mm. end view angles granulate, rounded, 



erasum** 



nn. Diameter ^fa^ in. (25^) or less pygmceum, 128 



nn. " greater than -^-^ ln - ( 2 5/0; en d broadly truncate, 

 sides slightly convex or nearly straight, converging, 



botrophilum, 131 



nn. Diameter greater than y-oVtf in. (25/^)5 end rounded, sides convex; 

 semi-cell elliptic .... rugulosum, 127; punctulatum, 127 

 co. End view 3-radiate or angular, sides nearly straight (//). 

 00. " sides concave (rr). 



00. End view 4-radiate or angular (xx). 



pp. Cells spinulose on the whole surface .... aculeatum, 140 

 pp. on the margins only setigerum, 141 



*Journ. R. Micr. Soc., Feb. 1886. 

 **F.-w. Algae, p. 42 et seq. 



