10 



LICHEN FLORA OF THE UNITED STATES 



<£7 ' jf--. 



Figure 4 



Cyphellae: Diagram 1, a section of the thallus of a Sticta; e, a cyphella composed of a net- 

 work of hyphae and protruding from an opening in the lower cortex of the thallus. Diagram 2, the 

 form of cyphella found in Sticta damaecornis, consisting of a depression in the lower side of the 

 thallus and surrounded by hyphae composed of almost spherical cells. In diagrams 1 and 2 the 

 usual layers of the thallus are shown; a, the dermis; b, the upper cortex; c, the algal layer; d, the 

 lower cortex; between c and d, the medullary layer; /, the rhizoids. Diagrams 1 and 2 enlarged 

 400 diameters. From Schneider. 



