tort] HERRE—DESERT LICHENS 207 
fectly at home in the midst of the most adverse desert conditions 
of excessive light and dryness is shown by the fact that almost 
everywhere the rocks are just as thickly covered with lichens as in 
other regions of greater humidity and less sunshine. The desert 
does not lack in number of individuals, but in number of species 
of lichens able to adapt themselves to its conditions. 
OAKLAND, CALIFORNIA 
