Ch. V] WARM TEMPERATE MOIST WINTER DISTRICTS 513 



It were premature to attempt to interpret, on the basis of available 

 climatic data, the above-mentioned peculiarities of sclerophyllous plants 

 and of their communities, and, in particular, the distinctions between them 

 and other xerophytes. There is a wide field open for exact physio- 

 logical research into this matter. Yet we are already in a position to 

 demonstrate with probability the utility of the most striking character of 



FlG. -'74. Sclerophyllous flora of California. Umbellularia californica (Lauraceae'. Natural size. 

 From a specimen in Prof. Dudley's Herbarium. 



sclerophyllous plants, their evergreen foliage. Vegetation in sclerophyllous 

 districts, as a matter of fact, is subject to only short yet frequent and 

 irregular periods of rest, and these are sometimes due to the cold of winter, 

 and sometimes to summer drought ; at the same time, only short periods 

 afford optimal conditions in regard to temperature and moisture. More- 



SCHIMPER L 1 



