PLATE XVIII. 



FIGS. PAGE 



1. Closterium aceromm (Schrank) Ehrenb. var. 



clongatumKveb. x 220 . . .148 



2-5. 01. acerosum (Schrank) Ehrenb. 2 and 3, x 

 200 (after Balfs) ; 4, extremity of a cell 

 showing' slight truncation, x 520; 5, zy go- 

 spore, x 200 (after Ralfs) . .146 

 0. CL aceroKHin var. angolensr, West & G. S. West. 



x 220 ... 149 



7. CL lanccoltttnin Kiitz. Zygospore, x 220 . 149 



s <)._ Cl. Luii nl<. Ehrenb. x 220 . . 150 



10. Cl. Lnnnln var. colonitum Klebs. x 120 . 152 



1 1 . CL L'H'nula var. biconvexnm Schmidle. x 120. 152 



12. Cl. Lunula var. intermedium Gutw. x 120 . 152 



