PLATE LXXII. 



FIGS. PAGE 



1-2. Cosmarium abruptum Lund. 1, x 400 (after 



Lundell; 2, x 520 . . . 80 



3. C. sexangulare Lund. x 400 (after Lundell) . 81 

 4-5. C. sexangulare forma minima JSTordst. 4a, 

 x 570 (after Nordsteclt) ; 46, x 500 ; 5, 

 x 1000 . . . .82 



6-8. C. pseudoprotuberans Kirchn. 6, x 410 (after 



Nordstedt) ; 7, x 520 ; 8, zygospore, x 520 . 82 

 9-11. C. abbreviation Racib. 9, x 1280 (after Raci- 



borski); 10 and 11, x 520 . . 84 



12. C. abbreviatum forma minor. x 520 . 85 



13. C. abbreviatum var. planctonicum W. & G. S. 



West, x 520. . . . 85 



14-18. C.impresxulumElfv. 14, x 500 (after Elfving) ; 



15-17, x 520; 18, x 600 (after Roy & Bissett) 86 

 19-21. C. umbilicatum Liitkem. 19, x 1000 (after 



Lutkemiiller) ; 20, x 500; 21, x 1000 . 88 



22-23. C. perpusillum West, 22, x 600; 28, x 1000 88 

 24. C. perpusillum forma, x 520 . . 89 



25-28. C. Regnellii Wille. 25, x 480 (after Wille) ; 



26-28, x 520 . 89 



29-32. C. Meneghinii Brett 29, x 400 (after Ralfs) ; 



30 and 31, x 520; 32, zygospore, x 520 . 90 

 33. C. quadratulum (Gray) De Toni. x 520. [Con- 

 sult PL XCIII, fig. 4.] . . .121 

 34. C. Meneghinii var. nanum Wille. x 320 (after 



Wille) . . . .93 



35-36. C. angulosum Breb. 35, x 350 (after Bre- 



bisson) ; 36, x 500 . .93 



37-38. C. angulosum var. concinnum (Rabenli.) W. & 



G. S. West, x 520 . . .94 



39. C. obliquum Nordst. forma major Nordst. x 500 51 

 40-41. C. pseudarctoum Nordst, Zyo-ospores, x 500. 



[Consult PI. LXYIII, figs. 12-14.] . . 32 



