Botanical Features of North American Deserts. 23 



Publication 99 of the Carnegie Institution by Dr. D. T. 

 MacDougal, under the title, "Botanical Features of North 

 American Deserts," embodies the results of explora- 

 tions in the arid southwest in connection with the founding 

 of the Desert Laboratory, together with later explorations there 

 and in Mexico by the author. 



The first third of the work is devoted to an account of the 

 topography and botanical features of the leading divisions of 

 the great desert region lying, as to its general east and west 

 boundaries, between western Texas and the Coast Range in 

 southern California, the most northern division being the sage 

 brush desert of Nevada and Utah and the most southern the 

 cactus region of Tehuacan in Mexico. In most cases it is possible 

 to characterize each of these regions by some prominent topo- 

 graphical feature, together with the dominance of certain plants. 

 Thus the sotol region of Texas is particularly marked by the 

 presence of Dasylirion texanum and Agave lechuguila. The 

 Otero basin in New Mexico includes a great salt and soda flat 

 and the "white sands,'' on which Rhus trilobata and Yucca 

 radiosa are among the dominant species. In the region of 

 Tehuacan the cacti are more abundant than in any other part 

 of the world, their massive forms constituting a prominent 

 feature of the landscape. In the sage-brush deserts of Nevada 

 and Utah Artemisia tridentata is dominant over wide areas, 

 which are further characterized by the rarity or absence of 

 succulents and plants with storage structures. The great tree 

 yucca, Yucca arborescens, forms the most striking feature of the 

 Mojave desert, while Larrea and Gaertneria constitute the char- 

 acteristic vegetation of wide mesas in Death Valley. In the 

 Salton basin, with a precipitation of only about 3 inches a 

 year, distinctively arid conditions prevail. Large areas are 

 almost bare of vegetation, but in moister and more alkaline 

 spots there is a considerable growth of Allenrolfea, Sueda and 

 A triplex, while the leached gravelly slopes exhibit a variety of 

 woody perennials. 



Passing from this general survey of the topographical and 

 botanical features of the wide area under consideration, the au- 

 thor presents in more detail a study of aspects of vegetation 

 in the neighborhood of the Desert Laboratory, giving an account 

 in succession of winter annuals and perennials, spinose and sue- 



