1907] / Hall. Compositae of Southern California. 9 



Sir William Dotting Hemsley, of the Royal Botanic Gardens 

 at Kew, England, has kindly supplied notes concerning certain 

 Asters and a sketch of the type of Aster Menziesii. Professor B. 

 L. Robinson, of Harvard University, has compared a number of 

 specimens with types at the Gray Herbarium, and supplied 

 valuable material for examination. Dr. J. N. Rose has loaned 

 specimens from the U. S. National Herbarium for comparison. 

 Dr. J. M. Greenman, of the Field Museum of Natural History, 

 has furnished critical notes concerning certain troublesome 

 Senecios. To all of these gentlemen I return my most sincere 

 thanks. 



Acknowledgment is also here made of aid received through 

 the Experiment Station of the University of California from the 

 "Adams Fund" of the United States Government. By means 

 of this aid a botanical trip was made through portions of the 

 Mohave Desert and Iriyo Co. in May and June of 1906. Although 

 primarily for the purpose of making studies in forage and stock- 

 poisoning plants, concerning which reports will be issued later, 

 much data here utilized was also obtained on the expedition. 



GEOGRAPHIC DISTRIBUTION. 



It has been found that in discussing the distribution of plants 

 or animals over any considerable area it is conducive to clearness 

 to have that area mapped into life zones, these being essentially 

 thermal belts recognized by the plant growth and animals which 

 they sustain. The following life zones are recognized in South- 

 ern California : 



Alpine, or Arctic-Alpine Zone. 



Huclsonian Zone. 



Canadian Zone. 



Transition Zone. 



Upper Sonoran Zone. 



Lower Sonoran Zone. 



The Arctic-Alpine Zone is sharply marked and consists only 

 of the Alpine flora above timber line. The only Compositae of 

 our district restricted to this zone are : 



Erigeron compositus discoideus Antennaria media. 

 Baillardella argentea. 



