SPECIES OF DESMIDS. 87 



I. Length twice the width or less; cytioderm punctate or granulate {a). 



I. " " " " " " cytioderm smooth (i^). 



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



costatus, 5 6 

 I. Length zj^ or 3 times the width; cytioderm punctate (c). 



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



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



pseudoconnatus, 55 

 2. " " " " " " cytioderm smooth, 



Thwaitsii, 5 6 



a. Semi-cell subquadrate ... Ralfsii, 54 



a. " cylindrical, rounded; constriction slight . cuciirbita, 54 



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



a. " 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, 



Clevei, 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 {h). 



2. " more or less verrucose or granular (z). 



a. Chlorophyll diffused (b). 



a. Chlorophyll concentrated in i or more nuclei (e). 



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



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



c. Margin crenate (s). 

 c. " undulate (/). 



c. " granulate (u). 



e. " dentate or notched; end truncafe, 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^ or less than twice longer than wide [k). 

 d. Cells less than i^ times longer than wide (/«). 



*F.-\v. AlgEE, p. 27. 



