PLATE CXXV. 



FIGS. PAGE 



1-2. Staurastrum orbiculare Ralfs var. extensuvn 



Nordst. x 520 . . .158 



3-5. St. suborbiculare W. & G. S. West. 3 and 4, 

 x 400 ; 5, zygospore, x 400 (after Roy & 

 Bissett) . . . .159 



Q-l.St. retusum Turner. x 520 . . 160 



8. St. retusum var. l>or^ale W. & G. S. West. x 



400 . . . . . 160 



9. St. tortum (Lagerli. & Nordst.) W. & G. S. 



West, x 800 (after Nordstedt) . .161 



10. St. tortum forma frigona G. S. West, x 430 . 162 

 11-12. St. cosmarioides Nordst. 11, x 400 (after 



Nordstedt) ; 12, x 400 . . .161 



13-16. St. subpygmseum West. 13, 14, and 16, x 520; 



15, x 400 . . . 162 



17-18. St. corniculatum Lund. 17, small forms, x 430 ; 



18, x 400 (after Lundell) . .163 



19-22. St. corniculatum var. spinigerum West. 19, x 



400; 20-22, x 500 . .164 



