EXPLANATIONS AND REFERENCES, 

 PLATE CLXXVII. 



Figures mostly magnified 2.50 diameters. 



PAGE. 

 Figs. 1, 2. MASTIGONEMA forms, somewhat distinct in the heterocysts and 



in the fihrillose sheaths, . . . 242 



'* 3, 4. more common forms, .... 242 



" 5, 6. ISACTIS FLUVIATILJS, two small sections of crust on rocks, . 245 

 Fig. 7-10. " *' , isolated trichomes separated from the crust, 245 



" 11. MASTIGONEMA AERUGINEOM, elongated form, . '42 



" 12. <l " turgid specimens, . . 242 



" 13. " " heterocysts wider than the tri- 



chomes, . . . 242 



" 14. CALOTHRIX CRUSTACEUM, section of thallus representing the 



Zonotrichia condition, . .240 



" 15. " " natural size of thalli, often many 



clustered together ; fig. 1 4 is a section 

 of one of these magnified, . 240 



