252 



STRUCTURAL BOTANY 



FIG. 104. Physcia pulverulenta. Portion of a vertical section 

 of the thallus, showing a complete carpogonium. a, projecting 

 trichogy^ne, with swollen gelatinous cell-wall, in which numerous 

 spermatia are caught ; e, coiled, ascogonial part of the carpo- 

 gonial filament ; b, dead layers of upper cortex ; c, living cortical 

 hyphae ; d, groups of gonidia ; /, medullary layer ; g, lower 

 cortex; h, rhizoids. Magnified about 1100. (After Darbi- 

 shire.) 



