PLATE XI. 

 [Proc. Wash Acad. Sci., Vol. Ill, PI. XLIV.] 



Fig. I. Cosmarium intermedium Delp. 



2. Euastrum elegans (Breb.) Kuetz. 



3. Penium digitus (Ehrenb.) Breb. 



4. Cosmariutn latum Breb. ■> 



5. Staurastrum dejectum Breb. a, b and c. -> 



6. Cosmarium sfhalerostichum Nordst. 



7. Micrasterias truncata (Corda) Ralfs. 



8. Cos7narium phaseolus Breb. 



9. Cosmarium undulatum Corda. 



11. Micrasterias denticulata (Brdb.) Ralfs. 



12. Cosmarium pachydermum Lund. 



13. Tetmemorus brcbissonii (Menegh.) Ralfs. 



14. Artkrodesmus cojivergens Ehrenb. 



15. Cosmarium blyttii Wille. 



16. Cosmarium coutractum Kirch. 



17. " kitckelii Wolle. 



i8. Xanthidium armatum (Breb.) Ralfs. 



19. Cosmarium tnetteghinii braunii {'^e'lnsch.) Hansg. 



20. Pleurotceniopsis debaryi (Archer) Lund. 



21. Cosmarium tumidum Lund. 



22. " ralfsii'Qx€h. 



23. Micrasterias kitckelii Wolle. 



24. Euastruin didelta (Turp.) Ralfs. 



25. " elegans (Brdb.) Kuetz. 



26. " " " Two forms. 



27. Micrasterias oscitans pinnatifida (Kuetz.) Rabenh. 



28. Cosmarium holmiense Lund. 



29. Staurasirum ravenelii "Wood, a, front view; b, end view. 



30. Euastrum elegans, large form. 



31. Micrasterias Jimbriata elephanta Wolle. 



[450] (214) 



