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OUTLINE OF PLANT GEOGRAPHY 



ranches with luxuriant fields of alfalfa and other crops, and fine 

 orchards. The contrast between the forest growth of some of 

 these sheltered canyons, and the barren desert without, is quite 

 extraordinary. 



As the lower slopes of the Sierra and the Cascades are reached, 

 the effect of the increasing moisture is seen in the greater number 

 of trees as one ascends toward the summit of the ranges. Although 

 the eastern slopes of the Sierra are much drier than those of the 

 Pacific side, nevertheless there is an abundant growth of fine 

 trees in which the yellow pine predominates. 



This intermediate region is well shown near Lake Tahoe, 



-Desert vegetation, Utah. Sage-brush {Artemisia sp.), Chrysothamnus 

 sp. Photo., Mr. Fred Buss. 



which lies at about 6,000 feet elevation on the boundary between 

 Nevada and California. About the eastern shore, the yellow pine 

 is the commonest tree, and sage-brush and other xerophytic plants 

 occupy the ground between the trees. On the western side, es- 

 pecially at the northern end of the lake, the effect of an extremely 

 heavy snow-fall is seen in a forest of mixed conifers, in which 

 the white fir (Abies concolor), is the commonest species, with 

 sugar pine (P. Lambertiana) , yellow pine, and incense cedar (Li- 



