328 THE AMERICAN NATURALIST. [Vol. XXXVI 1 1. 



the report of their journey, undertaken early last year, which took 

 them over most of the desert regions of the western part of this con- 

 tinent. The place decided on for the laboratory was a site about two 

 miles from Tucson, Arizona, and since then the laboratory has been 

 built and equipped. Besides the fact that the country around Tucson 

 is of a distinctly desert type and the flora as varied as such a flora is 

 apt to be, the practical questions of accessibility and of habitability 

 were considered. With the two authors as advi-sory board, Dr. W. 

 A. Cannon was appointed resident investigator and is at present 

 engaged on various researches. Arrangements have also been made 

 so that a limited number of trained investigators may avail themselves 

 of the privileges of the laboratory. " Not the least important part of 

 the duties of the resident investigator will be to aid visiting botanists 



This contribution besides containing a description of the trip under- 

 taken for the purpose of selecting a site for the laboratory, also 

 includes an account of the general botanical and climatic features 

 of the deserts of the regions visited. While the two authors had 

 both separately made trips to many of the same districts of the west, 

 the itinerary of their present journey included almost all of the arid 

 regions of the United States and of northern Mexico. Starting at El 

 Paso they first made their way down to the sand dunes of Chihuahua, 

 south of Samalayuca in Mexico. The winter vegetation of these sil- 

 iceous sand hills is scanty, only a few forms are mentioned. The 

 next point of attack was the Tularosa desert lying westward of 

 Alamogordo, New Mexico, the most interesting feature of which is 

 the region known as the White Sands, composed of drifting sand that 

 is almost wholly gypsum. The characteristic plant of the dunes is 

 Rhus trilobata, the roots of which bind the sand so effectually that 

 clumps of the plant bring about the formation of pillars of sand when 

 the surrounding dunes shift. A curious relation of plants of Yucca 

 radiosa to the dunes was also noticed. Investigation showed that a 

 Yucca growing out of the top of a thirty-foot dune, must penetrate 

 with its trunk to the bottom. On excavating it appeared that the plant 

 must have grown as the dune engulfed it. In the bottoms among the 

 dunes the vegetation is much denser, a grass is plentiful and Ephedra 

 is frequently met with. 



Tucson was next visited, there the woody vegetation of the desert 

 consists mainly of the creosote bush, the mesquite, joint pine, and 

 several Cactus forms, while higher on the foot hills occur the giant 

 Cereus, and species of the tree known as the palo verde. At the 



