TUCSON AS A LABORATORY SITE I3 



Some of our deserts, such as the Mohave, the Colorado, and the 

 lower part of the Gila, are of such extreme aridity that only a small 

 number of vegetative types occur in them. The same paucity of vege- 

 tative types is usually characteristic of any flat area of desert as distin- 

 guished from a foothill, canyon, or mountain area, a broken and rocky 

 soil giving a wider range of temperature and moisture conditions of 

 both soil and air, and furnishing lodgment for a greater variety of 

 plants. The yucca plains of the Tularosa desert in New Mexico and 

 the sage plains along the Snake and Columbia rivers in Idaho, Wash- 

 ington, and Oregon are examples of deserts in which a pronounced 

 paucity of woody species is correlated not with extreme conditions of 

 aridity but with flatness of surface. 



The members of the Board are acquainted with several charming 

 situations in the mountains of the desert, remote from civilization, rich 

 and remarkable in their flora, furnished with an abundance of pure 

 never failing water, and altogether delightful in their surroundings. 

 Such situations are often chosen for army posts and they are and will 

 always remain treasure spots for the camping naturalist. For the pur- 

 pose of a laboratory, however, they are objectionable for several rea- 

 sons. Such a situation involves first of all the maintenance of a hotel 

 or its equivalent, a feature that would tend to exhaust the financial and 

 mental resources of the management of a laboratory. Furthermore, 

 severe isolation for long periods would doubtless have a depressing 

 instead of an exhilarating effect on some research workers, and the 

 solicitude of friends and relatives would doubtless in some cases be a 

 bar to residence at such a place. 



The conditions of living at some spots in the desert suitable in 

 other respects for laboratory purposes are so severe as to offer an 

 obstacle to the best work. A period of such extreme heat as occurs in 

 summer at some points of very low elevation, as for example along the 

 lower Colorado river or in the vicinity of Guaymas, Sonora, or the 

 difiiculty of getting pure water and good food, has been an effective 

 argument against some otherwise good locations. 



Viewed from the standpoint of these primary requirements Tucson 

 has a climate of a thoroughly desert character, and a flora, including 

 mountains and plain, rich in species and genera. In addition to its 

 situation in the heart of the desert of Arizona, it is centrally located, 

 both as to position and transportation, with reference to the deserts of 

 Texas, Chihuahua, New Mexico, California, and Sonora. The city 

 has a population of about 10,000. It is situated on a transcontinen- 

 tal railroad, the Southern Pacific, less than four days' railway travel 



