SPECIES OF DESMIDS. 87 



i. Length twice the width or less; cytioderm punctate or granulate (a). 



i. " " " " " " cytioderm smooth (). 



i. " " " " " " cytioderm with 5-7 costae, 



costatus, 56 

 i. Length 2^2 or 3 times the width; cytioderm punctate (c). 



1. " 4 to 6 times the width; cytioderm smooth . minutus, 54 



2. Cell twice or more longer than wide; cytioderm punctate, 



pseudoconnatus, 5 5 

 2. " " " " " cytioderm smooth, 



Thwaitsii, 56 



a. Semi-cell subquadrate Ralfsii, 54 



a. cylindrical, rounded; constriction slight . cucurbita, 54 



a. " constriction wide, shallow . . connatus, 55 



a. u sub-semicircular; constriction slight; ends rounded or 

 somewhat truncate; end view circular . . . Cordanum, * 



b. Cell somewhat fusiform, ends subconically rounded . curtus, 54 



b. Cell subcylindrical, ends broadly rounded . . . diplospora, 56 



c. Cell subcylindrical, ends rounded; nuclei large, single or double, 



C levei, 56 



17. COSMARIUM. FIG. 17. 



End view without central inflations (i). 



End view with central inflations (2). 



i. Cytioderm smooth or punctate (a). 



i. more or less verrucose or granular (/). 



1. spinous (g). 



2. Cytioderm smooth or punctate (ti). 



2. more or less verrucose or granular (i ). 



a. Chlorophyll diffused (b). 



a. Chlorophyll concentrated in i or more nuclei (<?). 



b. Margins crenate, undulate, dentate or granulate (c). 



b. not crenate, undulate, dentate nor granulate (d). 



c. Margin crenate (s). 

 c. " undulate (/). 



c. " granulate (//). 



e. " dentate or notched; end truncate, smooth; sides toothed, 



convex Reinschii, 68 



e. Margin dentate; end 4-spined; sides smooth, convex, aculeatum, 66 



d. Cell twice or more longer than wide (/). 



d. Cell i l /2 or less than twice longer than wide (/'). 

 d. Cells less than 1^/2 times longer than wide (;;/). 



*F.-w. Algse, p. 27. 



