PLATE XI. 



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



FIG. I. Cosmarium intermedium Delp. 



2. Ruastrum elegans (Breb.) Kuetz. 



3. Penitim digitus (Ehrenb.) Breb. 



4. Cosmarium la turn Breb. 



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



6. Cosmarium sphalerostichum Nordst. 



7. Micrasterias truncata (Corda) Ralfs. 



8. Cosmarium phaseolus Breb. 



9. Cosmarium tmdulatum Corda. 



11. Micrasterias denticulata (Bre"b.) Ralfs. 



12. Cosmarium pachydermum Lund. 



13. Tetmemorus brcbissonii (Menegh.) Ralfs. 



14. Arthrodesmus convergens Ehrenb. 



15. Cosmarium blyttii Wille. 



16. Cosmarium contractum Kirch. 



17. " kitchelii^No\\z. 



18. Xanthidium armatum (Breb.) Ralfs. 



19. Cosmarium meneghinii braunii (Reinsch.) Hansg. 



20. Pleurotczniopsis debaryi (Archer) Lund. 



21. Cosmarium tumidum Lund. 



22. " ralfsii Bre"b. 



23. Micrasterias kitckeliiVfo\\e. 



24. Euastrum didelta (Turp.) Ralfs. 



25. " elegans (Bre'b.) Kuetz. 



26. " " " Two forms. 



27. Micrasterias oscitans pinnatijida (Kuetz.) Rabenh. 



28. Cosmarium holmiense Lund. 



29. Staurastrum ravenelii Wood, a, front view; , end view. 



30. Euastrum elegans, large form. 



31. Micrasterias fimbriata elephanta Wolle. 



[450] (2I 4 ) 



