PLATE CXXXVIII. 



FIGS. PAGE 



1-3. Staurastrum pilosum (Nag.) Arch. 1, X 520 

 (vertical view in outline only) ; 2, zygospore, 

 X 400 (after Wittrock), cf. footnote, p. 64 ; 

 3*, X 510 . . .63 



4-6. St. hirsutum Breb. 4, X 500 ; 5, X 460 ; 6, forma 

 minor, zygospore, X 550 (from a drawing by Dr. 

 Liitkemiiller) .... 65 



1-8. St. Ravenelii Wood. 7, X ? (after Turner) ; 8*, 

 forma X 810 (from Wittr. & Nordst. 'Alg. Exs.' 

 no. 1477) . . . 70 



9. St. muricatum Breb. X 520 . . .67 



10-12. St.pyramidatumWest. 10, vertical view, X 520; 



11 and 12. X 520 . . . 68 



13. St. pyramidatum var. coilon West. X 400 (outline 



only) . . . . .69 



