EXPLANATIONS AND REFERENCES, 

 PLATE CLXXIV. 



PAGE. 

 Fig. 1. MASTIGONEMA HALOS, the plant enlarged 250 diameters, . 242 



2. under low magnification, . . 243 



" 3-9. MASTIGONEMA AERUGTNEUM, in varieties, . . . 241 



'' 3-4. distinct forms with twin hetero- 



cysts, .... 241 



" 5-7. with pyriform heterocysts, . 241 



" 8. spherical, single heterocysts (M. 



fibrosa), . . . 244, 241 



" 9. MASTIGONEMA ELONGATUM, .... . 243 



