1904] FINK—A LICHEN SOCIETY 277 
because of proximity, get possession often of considerable portions 
of the rocky substratum. Excepting the Stereocaulon, there seems 
to have been in the present instance a pretty nearly equal struggle 
for place in the society, those lichens that are best adapted to the 
ecologic conditions gaining the ascendency, and entirely or nearly 
completely crowding out those less well adapted. That gaining pos- 
session is by no means a matter of pure chance will appear in the 
discussion next below of an adjacent society of a southward exposed 
riprap. 
Fic. 4.— Stereoca 
ay 
ulon paschale on a riprap block on the upper surface and toward 
the base of one of the es : 
extensions. 
‘h The Amphiloma-like thallus has been purposely omitted from 
*S€ considerations of origin of the floral elements of the society, 
Since oe ‘ ‘ x ‘ 
ta ie very definite statement can be made till the species is ascer- 
‘dinec . 
VIL, COMPARISONS WITH OTHER SIMILAR SOCIETIES. 
7 A. The society of a neighboring riprap. 
: mh a number of ripraps at various places along the south 
Well as sie tailroad bed, and all of these have been examined, as 
'S on the north side, the one selected for the present study 
sid 
