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narrow belt along the western slope of Antelope Valley. The 
normal flora of the desert slopes is modified in this section by the 
presence of such species as Pinus Sabiniana, Quercus Douglasit, 
Grossularia quercetorum and Aesculus californica. 
Along the Mexican Boundary a number of Peninsular species 
enter the flora in the pifion belt. Of these Pinus quadrifolia is the 
most noteworthy. This nut pine, which almost entirely replaces 
Pinus monophylla a few miles below the international boundary, 
occurs sparingly as far north as the Santa Rosa Mountains. 
The following are the characteristic Upper Sonoran trees and 
shrubs of the desert slopes: 
*Pinus monophylla Isomeris arborea globosa 
*Pinus quadrifolia *Kunzia glandulosa 
Juniperus californica *Rhamnus cuspidata 
Juniperus utahensis * Ceanothus vestitus 
Ephedra viridis Malacothamnus Fremonti 
*Quercus Alvordiana *Fremontodendron californicum 
*Quercus Dunnit Fraxinus velutinus 
*Quercus turbinella Fraxinus anomala 
Eriogonum fasciculatum polifolium Diplacus aridtis 
*Eriogonum Heermaniu Stenotopsis interior 
*Odostemon Fremontit 
The species designated by an asterisk (*) are confined to the 
upper or pinon belt. 
Lower AusTRAL ZONE 
General description—The Lower Austral Zone in southern 
California is represented by the Lower Sonoran Area. It includes 
all of the desert regions below the juniper belt, and protrudes 
through the lower passes into the hot interior valleys of the coastal 
slope. It also extends northward along the coast of Lower Cali- 
fornia to the vicinity of San Diego. 
Three floral elements enter into the composition of the Lower 
Sonoran in southern California, the Great Basin, the Sonoran, 
and the Peninsular. In the Mohave Desert many of the charac- 
teristic species are of the Great Basin element, in the Colorado 
Desert the Sonoran and the Peninsular species predominate, 
and at San Diego the Peninsular. Unfortunately the Lower 
Sonoran Area has not been sufficiently explored to warrant its 
division into sub-areas. Each of the southern California sections 
