1907] * Hall. Compositae of Southern California. 11 



portion of the San Bernardino Plains, where are found desert 

 immigrants that have undoubtedly come by way of Cajon Pass ; 

 and portions of southwestern San Diego Co., where desert species 

 have established themselves, coming either through low passes 

 from the Colorado Desert or northward from Lower California. 

 The plants of this zone are nearly all xerophytes with various 

 adaptations to their arid habitat. The following common Com- 

 positae are characteristic of this zone : 



BricTcellia atractyloides Baileya pauciradiata 



Acamptopappus sphaerocephalus Chaenactis carphoclinia 



Ericameria monactis Porophyllum gracile 



Chrysothamnus paniculatus Dysodia Cooperi 

 Chrysothamnus nauseosus graveolens Pectis papposa 



Monoptilon bellioides Artemisia spinescens 



Aster Mohavensis Peucephyllum Schottii 



Aster spinosus Lepidospartum squamatum 



Baccharis sergiloides Tetradymia spinosa 



Franseria dumosa Malacothrix glabrata 



Life areas differ from life zones in that they indicate all of 

 the factors influencing the distribution of life, rather than only 

 that of temperature. Three life areas may be distinguished in 

 Southern California, namely, the Desert Area, the Nevadan or 

 Montane Area, and the Cismontane Area, the last including 

 everything southwest of the principal mountain chain. These 

 areas may be subdivided into subareas, for example, the Mohave 

 and Colorado subareas, the Coastal Subarea, etc. 



Various papers dealing with plant and animal distribution 

 in Southern California have been consulted in reference to this 

 subject, and especially the works of Dr. C. Hart Merriam, of the 

 Biological Survey, U. S. Department of Agriculture, who was 

 the first to distinguish and name the Life Zones of North America 

 according to our present system. Such papers are : 



C. HART MERRIAM: Life Zones and Crop Zones of the United States, 

 U. S. Dept. Agr., Div. of Biological Survey, Bull, ix (1898). 



C. HART MERRIAM : Eesults of a Biological Survey of the San Francisco 

 Mountain Region and Desert of the Little Colorado, Arizona, N. A. Fauna 



Xo. 3 (3890). 



C. HART MERRIAM: Results of a Biological Survey of Mt. Shasta, Cali- 

 fornia, N. A. Fauna No. 16 (1899), etc. 



S. B. PARISH : A Sketch of the Flora of Southern California, Bot, Gaz. 

 xxxvi. 203-222 and 259-279 (1903). 



