SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. 21 



senting a descriptive account of the region and much necessary- 

 information and statistics concerning its climatic character- 

 istics, the author enters into a discussion of the various phyto- 

 geographic areas into which it is naturally divided. He finds 

 that the whole of Southern California may be divided into three 

 primary areas. The first of these, termed the Nevaclan area 

 from the fact that its flora is in the main a continuation of that 

 of the Sierra Nevada Mountains, extends in a Northwest and 

 Southeast direction and includes all of the truly montane sec- 

 tion, as well as all the forests of the territory. To the East and 

 Northeast is a treeless waste, or desert area, while a Cismontane 

 area of open plains and chaparral-covered hills occupies the 

 territory between the Nevaclan area and the Pacific ocean. 

 Above the Nevadan area traces of an Arctic-Alpine zone are 

 recognized on Grayback and San Jacinto mountains. The flora 

 of this zone is likewise of northern origin and the reasons for its 

 exclusion from the Nevadan area are not stated. Within the 

 NTevadan area proper three life zones are distinguished: the 

 Hudsonian, marked in general by Pinus flexilis; the Canadian, 

 roughly indicated by Pinus Murrayana; and the Transition, 

 best identified by the presence of Pinus ponderosa. The last of 

 these zones is the most important and includes, besides the pine 

 just mentioned and its variety Jeffreyi, such conifers as Abies 

 Douglasii, Libocedrus decurrens and Pinus Lambertiana. 



Just below this pine belt and above the belt of chaparral 

 there occurs what the author terms an intermediate, or true 

 Transitional zone. On the Desert side its most characteristic 

 plants are Juniperus Californicus and Cercocarpus ledifolius, 

 while within its limits such diverse species as Abies concolor and 

 Yucca brevifolia are found growing side by side, as also are 

 Pinus ponderosa and P. monophylla. On the cismontane flank 

 this belt is marked by the presence of Pseudotsuga macrocarpa 

 and Pinus Coulteri, the latter, however, extending well up into 

 the Pinus ponderosa belt. While this intermediate belt is m 

 most places quite narrow the author has done good service in 

 pointing out its presence and characteristics. Although it is 

 spoken of as a "true Transitional zone," it is not to be confused 

 with the broader and much more important zone next above, 

 which has been generally known as the Transition zone. 



The Desert area is divided naturally into the Mohave subarea 

 and the Colorado subarea. It is shown that the flora of the 

 former has its extension to the north while that of the latter has 

 its extension toward or into Mexico. The difference in the char- 

 acter of these tAvo floras is found to be due only in part to cli- 

 matic causes, but is largely influenced by the topography of the 

 region. The Cismontane area exhibits three more or less dis- 

 tinct floras, each of which is indicative of its peculiar subarea. 



