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1907] HERRE—LICHEN DISTRIBUTION 269 
The maritime area is sharply defined, more so in fact than any of 
the others, and includes not only a narrow strip of land all along 
the coast but also all of the northern tip of the peninsula down 
to and including the San Bruno mountains. Most of this area is 
of course of low elevation, but in the northern part of San Mateo 
County, where the broken hills of San Francisco culminate in San 
Bruno mountain, it extends to an altitude of more than 1300 
feet. 
This maritime region possesses the most equable climate of the 
peninsula, and also perhaps the highest daily average of humidity. It 
is characterized by relatively cold, windy, and foggy summers, the 
fogs mitigating the dryness of the rainless summer months; the winters 
are comparatively clear, sunshiny, with less precipitation than the 
redwood forests farther inland, and much warmer than in the other 
areas. At several points along the coast a whole winter often passes 
without the temperature once falling to 32° F. 
This area may (in a large way) be considered as a part of the belt 
which extends southward to the tropics, and beginning again on the 
coast of Peru reaches far to the south of Valparaiso, Chile. It is a 
region. in the main of slight rainfall and very moderate range of 
temperature, and it is therefore not surprising that we find a number 
of rock or earth lichens common alike to the shores of California, 
Peru, and Chile, yet unknown except on the Pacific coast of the 
Americas. 
I have no means of knowing how far to the north of the Golden 
Gate these forms go, but most of them, including those originally 
described by TucKERMAN from the San Francisco Bay region, seem 
to become more luxuriant as we go farther south, though I have seen 
none from below Guadalupe Island, Lower California. This would 
seem to indicate that such forms may be regarded as migrants from 
regions lying nearer to the tropics, and that the Golden Gate is very 
near to their northern limit, if indeed they go beyond it. In this 
category we may place most of the characteristic lichens of the 
maritime region. 
The characteristic lichens of this area do not occur in any of the 
other areas, and in that respect it is the most strongly marked of 
them all. Some of the more important are as follows: 
