PLATE CLV. 



FIGS. PAGE 



1-4. Staurastrum furcatum (Ehr.) Breb. 1, zygospore, 



X 400 (after Ralfs) ; 2, X 400 ; 3 and 4, X 500 173 

 5-6. St. furcatum var. candianum (Delp.) Cooke. 5, X 



about 400 (after Cooke) ; 6, X ? (after Delponte) 175 



7. St. furcatum var. subsenarium West. X 520 . 175 



8 St. arcuatum Nordst. X 400 (after Nordstedt) . 180 



9. St. arcuatum var. Guitanense West. X 400 . 180 



10. St. subavicula W. & G. S. W. X 520 . . 181 



II. St. amphidoxon W. & G. S. W. X 400. . 181 



12. St. Tohopekaligcnse AVolle. X 520 . 178 



13-14. St. Tohopekaligcnse var trifurcatum W. & G. S. W. 



13* X 510 ; 14, X 520 . . 179 



