KEY TO THE SPECIES OF THE DESMIDS. 



I. GONATOZYGON. 



1. Cells swollen at base, with 6 longitudinal lines of short seta, 



sex-spini/ei-um.'** 



2. Cells not swollen at base {a). 



a. With hair-like spines clothing the surface- . . . pilosum, 22 

 a. Without hair-like spines; surface minutely roughened, asperum, 22 



2. Genicularia.* Fig. 2. 



1. Cells 3^ to 6 times longer than broad; granules in spirals, 



Americana* 

 I. Cells 10-12 times longer than broad; granules scattered, spiroicenia* 



3. Hyalotheca. Fig. 3. 



I. Cells slightly constricted, length }4 the width, sides not notched, 



dissiliens, 2 2 



1. " " " " " sides arched, cen- 



trally notched . hians.** 



2. Cells slightly concave, length twice the width . undulata, 23 



3. Cells not co.istricted, margins straight; sheath wide, mucosa, 23 

 3. " " " " sheath absent, duhia, 24 



4. Bambusina. Fig. 4. 



1. Cells hub-shaped, somewhat longer than broad Brebissonii, 24 



2. Cells hub-shaped, nearly twice as long as broad gracilescens.** 



3. Cells subcylindrical, 4 times longer than broad ddicatissinia, 25 



*Journ. R. Micr. Soc, Dec, 1885, 

 **F. W. Alg£E, p. 21. 



