EXPLANATIONS AND REFERENCES, 

 PLATE CLXXIX. 



PAGE. 

 Fig. 1. RIVULARTA DURA, transverse section of a large thallus, . 249 



2. seel ion of a seml-thallus, developing spores, 249 



" 3. section of a semi-thallus, with trie-homes 



withering, .... 249 



" 4. RIVULARIA ECHINULATA, one of a floating mass of thalli, . 249 



" 5. " " natural size of thalli, . . 249 



" ti. GLOEOTRICHIA PISUM, thalli of natural size, . . . 247 



7. peculiar condition ; endochrome passing 



down into the basal heterocysts, . 247 



Figs. 8, 9. small sections of other thalli not empty- 



ing in the same manner, . . . 247 



Fig. 10. GLOEOTRICHIA NATANS, two trichomes, apparently in a state of 



dissolution, .... 247 



11. trichomes with long spores, narrow 



sheath ; gonidia passing out at rup- 

 tured ends, . . . 247 



