290 



OHIO BIOLOGICAL SURVEY 



wliicli follows back into the cave as far as its particular light re(iuire- 

 iiieiit will i)erinit. A considerable number of species are freciuently 

 found in such habitats, but most of them must be classed as accidental. 

 Among the few which seem to have a somewhat definite place in such 



Fig. 24. ,\ Wit Ciivi' Occupied by Ferns ( 1 )ry(i]it('i-is niiiriiiiialc ct I), spiiuiliisnm ) ;is t';ir back 



as the Illuiiiiiiation Permits. Beyond them a Zone of Lidiens. In the Foregroinid 



a Dead Cane of Sambucus racemosus. 



habitats only three need Ye mentioned: Sainbticiis racemona, the red 

 elderberry, is oftentimes to be found only in such habitats, being appar- 

 ently crowded out of other habitats. Dryopteris marginalis and D. 

 spmulosa are, however, the most conspicuous and constant inhabitants^ 

 of the wet caves. They follow far back into the weak light where, 

 undisturbed l)y other vegetation, they form very beautiful and perfect 

 rosettes, conspicuously oriented, of course, toward the source of light 

 (fig. 24). Beyond the reach of any vascular plant is a zone of crustose 

 lichens which covers the surface of the rock fragments. 



THE GTHLI) OF SIIADE-LOVIXG EVERGREEN HERBS 



Most abundant on shaded i-ocks, tho often found in other 

 habitats, especially in tlu^ upland forest, is a guild of plants which 

 recpiires separate consideration. These are the prostrate or acaulescent 

 herbs with evergreen or hibernating leaves. They share the advantages 



