PLATE XCI. 



FIGS. PAGE 



1-2. Cosmarium retusum (Perty) Rabenh. 1, x 400 



(after Lundell) ; 2, x 500 . . 265 



3. C. retusum var. angustatum West & G. S. 



West, x 625. . . . 266 



4-5. C. insequalipelUcum West & G. S. West, x 520 266 

 6. C. Ungerianum (Nag.) De Bary. x 600 (after 



JSTageli) . . . .195 



7. C. Ungerianum var. subtriplicatum West & G. S. 



West, x 520 . . .196 



8. C. Oligogongrus Reinsch. x 720 (after Reinsch) 194 

 9. C. suUrinodulum West & G. S. West. x 520 218 

 10. C. pseudoprotuberans Kirch n. var. alpinum 



Racib. x about 2000 (after Raciborski) . 83 

 11. C. GrantiiTLoy & Biss. x 600 (after Roy & 

 Bissett). The description of this species is in 

 the next volume. 



12. C. quadrifarium Lund, forma polysticha nob. 

 x 520. [Consult PI. LXXVI, figs. 15-17, and 

 PL LXXVII, figs. 1-4.] . . 144 



13. C. polygonum (Nag.) Arch. var. exile West & 

 G. S. West, x 520. Individual with a 

 curious stalk-like prolongation from one 

 angle of the cell- wall. It was collected by 

 Welwitsch in Central Africa 76 



