MAMMALS OF THE MEXICAN BOUNDARY. 47 



the lu'ud of Cajoii Bonito Creek, in the San Lnis Mountains, west to 

 tlie Santa Cruz Valley. The lowest ])oint was in Sonora, near the 

 junction of Cajon Creek with the San Bernardino River (altitude 

 8,109 foot, or 1)75 meters) ; tlu- hiohest, near the head of Baboconieri 

 C'rcclv. in Arizona (altitude 5,320 feet, or 1,621 meters). 



SALIX LASIOLEPIS Bentham, 

 BIGELOW WILLOW, 



This Avillow is abundant on the Pacific slope of the Coast Range 

 Mountains, in California and Lower California. To the eastward 

 we obtained it only on the Huachuca Mountains, Arizona. 



SALIX NUTTALLII Sargent. 

 NUTTALL WILLOW. 



This is an alpine species, growing- near the summits of the Mogollon 

 and San Francisco mountains, in central Arizona, and on San Jose 

 Mountain, in Sonora, ]Mexico." 



POPULUS TREMULOIDES Michaux. 

 ASPEN; aUAKING ASP. 



Aspens were found only on the sunnnits of the Animas, San Jose, 

 and Huachuca mountains, where they belong to the highest or Boreal 

 zone, and are associated w4th Quercus ehrysolepis^ Q. gamhelii^ Phius 

 strohiformis^ and Pseudotsuga miterouata. Its vertical range, on the 

 Mexican Line, is frbm 1,343 meters or 7,690 feet (San Jose Mountain 

 Sonora, Mexico) to 2,887 meters or 9,472 feet (summit of Huachuca 

 Mountains, Arizona). The largest aspens were those on the Hua- 

 chuca peaks; but none of those seen on the Mexican Line were com- 

 parable in size Avitli the aspens of northeastern Arizona. At Little 

 Spring, at the north base of San Francisco Mountain, Arizona (alti- 

 tude 2,500 meters or 8,250 feet), I measured an aspen that was 1.72 

 meters (5.64 feet) in circumference and 21.3 meters (70 feet) in 

 height. 



POPULUS ANGUSTIFOLIA James. 



NARROWLEAF COTTONWOOD. 



This handsome cottonwood was collected at one or two places in 

 (xrant County, New Mexico, in the vicinity of springs, Avhere it may 

 have been artificially planted. It is a common tree in Tonto Basin. 

 Arizona. I had previously collected it on Fossil, Corduroy, and Car- 

 riza creeks, in central Arizona. 



"Another willow, which I am unable to deterniine. is abundant in moist 

 valleys near the suunnit of the Coast Ran^e. in California. This is a scrubby 

 tree from 2 to G meters (6 to 20 feet) in height. 



