1904] FINK—A LICHEN SOCIETY 281 
solid and less rapidly disintegrating surfaces at the “Ledges,” the 
somewhat better developed crustose thalli, as the Lecanoras, the 
Placodiums, the Pertusaria, the Urceolaria, and the Buellia, have to 
some extent replaced the less differentiated thalli such as the first 
two of the list for the riprap. Because the disintegrating sand- 
stone of the “Ledges” falls to the ground and is covered with water 
Fig, 5.—} 
‘atures and Sf 
a) : 
ortions of the “Ledges” on both sides of the stream, showing general 
ermatophytic flora. 
"yd away in high water, the Cladonias appear only 
The more ag of the ledge faces and are cop EE nee. 
and the Frti a occurrence of the foliose Parmelias and Physcias 
Mote shaded aap Ramalinas at the “Ledges” is due partly to the 
surroundin na moist conditions, and in part to the presence * 
The abo list from which they may easily wander to the rocks. 
Parison of the two societies is the more interesting 
ted that both are growing upon the ferruginous sand- 
‘ame geological horizon, and that the differences noted 
ve com 
Wi . : ° 
NEN it is state 
