STRATOSE-RADIATE THALLUS 



117 



areas or granules as in Cl. pyxidata (Fig. 69) and others. In CL degenerans, 

 the spaces between the corticated areolae are filled in by loose filaments 

 without any green cells. CL rangiferina, CL sylvatica, etc. are non-corticate, 

 being covered all over with a loose felt of intricate hyphae. 



In the section Clathrinae (CL retepora, etc.) the cortex is formed of 

 longitudinal hyphae with thick gelatinous walls. 



d. SOREDIA. Frequently the podetium is coated in whole or in part by 

 granules of a sorediate character coarsely granular in CL pyxidata, finely 

 pulverulent in Cl. fimbriata. Though fairly constant to type in the different 

 species, they are subject to climatic influences, and, when there is abundant 

 moisture, both soredia and areolae develop into squamules on the podetium. 

 A considerable number of species have thus a more or less densely squamu- 

 lose "form" or "variety." 



C. DEVELOPMENT OF THE SCYPHUS 



Two types of podetia occur in Cladonia : those that end abruptly and 

 are crowned when fertile by the apothecia or spermogonia (pycnidia), or if 

 sterile grow indefinitely tapering gradually to a point (Fig. 70); and those 



Fig. 70. Cladonia furcata Schrad. Sterile thallus (S.H., Photo.). 



that widen out into the trumpet-shaped or cup-like expansion called the 

 scyphus (Fig. 69). Species may be constantly scyphiferous or as constantly 

 ascyphous; in a few species, and even in individual tufts, both types of 

 podetium may be present. 



