PLATE X. 



Figures magnlfled 300 diameters except Closterium, only 250 diameters. 



Page. 

 Figs. 1, 2. Closterium acbrosum, forma striolatum with single and twin 



zygospores, . . . .42 



Fig. 3. Closterium lineatum, Var. costatum, with twin zygospores, 45 



Figs. 4, 5. Arthbddesmus notochondrus, in front and vertical views, . 105 



Fig. 6. AhTHRODBSMUs INCBASSATUS, Var. cycladatus, . . 105 



Figs. 7, 8. CosmArium oculiperum, front and lateral views, . . 76 



" 9-1 1. Pesium CRDOirEBUM, in different stages of division, . 38 



" 12, 13. .\rthrodesmus pachtcerus, front and lateral views, . . 105 



14,15. Akthrodesmds TRIANGULARIS, front and vertical views, . 105 



Fig. 16. DociDiuM Georgicum, . . . . .55 



" 17. Penium spirostriolatum, var., . . . 35 



" 19. " " ..... 35 



•' 18. DOCIDIDM vebticillatum, . . . 58 



Figs. 20, 21. DociDiuM rectum, ... . . 52 



