16 



THALLOGENS. 



LiCHENES. — ^Aerial mycetals, chiefly nourished by the surround- 

 ing medium, and producing in the thallus, green bodies re- 

 sembling chlorophylle, termed gonidia, arranged singly, in 

 bundles, or moniliform rows ; fruit of sporidia, contained in 

 asci, or with secondary fructification, seated on sporophores j 

 containing — Cetraria Islandica, and Roccella. 



