PLATE XX. 



FIGS. PAGE 



1-5. Closterium Cornu Ehreiib. 1 and 1, x 400 ; 



3 and 4 ; x 520 ; 5 ; zygospore, x 400 . 157 



6-10. CL abruptum West. x 520. 10, zygospore . 158 

 11-12. CL abruptum var. brevius West & Gr. S. West. 



x 400 . . . . 160 



13_14._C7. toxon West, x 400 . . . 160 



15. CL Balmacarense Turn. x 400 (after Turner) 161 

 16. Cl. Balmacarenae forma minor Turn. x 400 



(after Turner) . . . .161 



17. CL Scoticum Turn. x 400 (after Turner) . 161 

 18. CL Scoticum var. fusiforme Turn. x 400 (after 



Turner) .... 162 



19. CL pusillum Hantzsch var. major Racib. . 163 



20-24. Cl. pusillum var. monoliihum Wittr. . .163 



