PLATE LXXVII. 



FIGS. PAGE 



1-3. Cosmarium quadrifarium Lund. 1, x 500; 2, 

 zygospore, x 400 (after Lundell) ; 3,, zygo- 

 spore, x 520. In fig. 1 small scrobiculations 

 are present between the central granules. 

 Fig. 3 shows a zygospore in which the two 

 angles at one end of the rectangular zygospore 

 are twisted in a plane at right angles to that 

 containing the other two . . 141 



4. C. quadrifarium forma liexasticlia (Lund.) 



Nordst. ' x 400 (after Lundell) . . 143 



5-6. C. dovrense Nordst. 5, x 500; 6, x 1000 . 144 

 7-10. C. isthmium West. 8 and 9, zygospores. 7, 

 x 500; 8-10, x 400. [Consult PL XCIV, 

 fig. 2.] ... 145 



11. C. istlimiiim forma hibernica West. x 500 . 146 



12. C. excavatum Nordst. x 1000 (after Nord- 



stedt) . . . .147 



13. C. subexcavatum West & G. S. West. x 400 



(after Wille) . . 148 



14. C. subexcavatum var. ordinatum West & G. S. 



West, x 520 . . .149 



15-17. C. orbiculatum Ralfs. 15, x 400 (after Ralfs) ; 

 16, x 400; 17, zygospore, x 400 (after 

 Balis) . 149 



18. C. orbiculatum forma major W. & G. S. West. 



x 400 . . . 150 



19. C. prxgrande Lund. x 400 (after Lundell) . 150 

 20-21. C. zonatum Lund. 20, x 400 (after Lundell) ; 



21, x 500 . . . 123 



22. C. binerve Lund. x 400 (after Lundell) . 123 



