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KEY TO THE GENERA BASED UPON THE 

 VEGETATIVE CHARACTERS. 



1. (35) Coloring matter not restricted to definite plastids 



Class Myxophyceae 2 



.?. (22) Cells solitary or in colonies, never in filaments 



Order Coccogoneales 3 



3. (12) Ceils solitary or in colonies that never contain more than 



a few cells 4 



4. ( 7) Cells spherical or hemispherical 5 



5. ( 6) Cells without a definite arrangement Chroococcus p. 27 



6. ( 5) Cells in a flat plate Merismopedia p. 31 



7. ( 4) Cells longer than they are broad 8 



8. (11) Individual cells not enclosed by a special gelatinous vesicle 9 



9. ( 10) Ends of cells rounded Rhabdoderma p. 46 



10. ( 9) Ends of cells pointed Dactylococcopsis p. 47 



11. ( 8) Individual cells or groups of cells enclosed by a gelatinous 



vesicle Gloeothece p. 45 



12. ( 3) Cells in colonies that contain many cells when mature 13 



13. ( 18) Cellular arrangement within colony definite 14 



14. ( 15) Cells forming a flat plate Merismopedia p. 31 



15. ( 14) Cells forming a hollow sphere one cell in thickness 16 



16. (17) Center of colony with radiating gelatinous strands 



Gomphosphaeria p. 36 



17. ( 16) Center of colony without radiating gelatinous strands 



Coelosphaerium p. 33 



18. ( 21) Cells spherical 19 



19. ( 20) Cells densely aggregated Microcystis p. 38 



20. ( 19) Cells some distance from one another Aphanocapsa p. 41 



21. ( 18) Cells longer than they are broad Aphanothece p. 43 



22. ( 2) Cells in simple or branched filaments. .Order Hormogoneales 23 



23. (30) Trichomes without heterocysts Family Oscillatoriaceae 24 



24. (29) Trichomes solitary or in flocculent readily dissociating 



masses 25 



25. ( 26) Trichomes containing but one spirally twisted cell 



Spirulina p. 49 



26. (25) Trichomes containing more than one cell 27 



27. (28) Sheaths of filament firm, generally projecting beyond the 



trichome Lyngbya p. 52 



28. ( 27) Sheath delicate or lacking, not projecting beyond the tri- 



chome Oscillatoria p. 50 



29. I 24) Trichomes laterally united to form free-floating bundles 



which do not dissociate readily Trichodesmium p. 54 



30. ( 23 ) Trichomes with heterocysts 31 



