PLATE CLXIV. 



FIGS. PAGE 



1-3. Desmidiwn Aptogonum Breb. 1*, X 510 ; 2*, 



vertical view, X 810 ; 3, zygospores, X 520 . 242 

 4-5. D. Aptogonum var. Ekrenbergii Kiitz. X 520 . 243 

 6. D. Aptogonum var. acutius Nordst. X 400 (after 



Nordstedt) . . . .244 



7-10. D. ci/lindricum Grev. 7* X 510 ; 8*. vertical 



i/ 



view, X 510 ; 9*, early stage in conjugation, 

 X 510 ; 10, ripe zygospore, X 520 . . 249 



11, -D. occidentals AY. & G. S. W. X 400 . . 245 



