EXPLANATION OF PLATES 



All of the figures of the following plates were drawn under the direction of the 

 authors by Ur. Helen M. Gilkey, Avith the exception of figures 5, 11, plat« 1, 

 5, 6, plate 8, and 30, plate 7, which were drawn by H. N. Bagley, and figures 

 8, 9, plate 8, figs. 15, 1(5, plate 1, drawn by Miss Almeda H. Nordyke. 



PLATE 1 



Plectonema Battersii Gomont 



Fig. 1. Plants with hormogonia just beginning false branching. X 500. 



Gomphosphacria aponina Kuetz. 

 Fig. 2. Surface view of a colony showing the ends of radiating filaments. 

 X 500. 



Fig. 3. A small fragment showing the branching stalks of the cells. X 500. 



Plwrmidium lucidum (Ag.) Kuetz. 

 Fig. 4. Terminal portion of a single filament. X 1000. 



SpiruUna major Kuetz. 



Fig. 5. Two filaments, one coiled loosely throughout, the other with one-half 

 very tightly coiled. X 1200. 



Synechococcus curtus Setchell 

 Fig. 6. Showing various stages of division. X 1000. 



Synechocystis aquatilis Sauvageau 

 Fig. 7. Small group of cells showing various stages of division. X 1000. 



Isactis plana var. plana B. and F. 



Fig. 8. Diagrammatic section showing perpendicular, parallel arrangement 

 of the filaments. X 12. 



Fig. 9. Section of the thallus showing the character of mature filaments. 

 X 250. 



Hydrocoleum lynghyaoeum Kuetz. 



Fig. 10. The end of a filament showing trichomes within the sheath. X 250. 



Oscillatoria acuminata Gomont 



Fig. 11. Three terminal portions of trichomes showing different degrees of 

 attenuation and uncination. X 500. 



Symploca hydnoides Kuetz. 



Fig. 12. A habit sketch showing characteristic, erect, attenuate fascicles. 

 X 10. 



Fig. 13. A single filament. X 500. 



Chroococcus turgidus f. siibmarimts Hansg. 

 Fig. 14. Showing one-, two-, and four-celled stages. X 250. 

 Fig. 15. Lynghya aestuarii f. natans Gomont. X 500. 

 Fig. 16. Lynghya aestuarii f. aeruginosa (Ag.) "Wolle. X 500. 



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