48 BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



POPULUS FREMONTII Watson. « 

 FREMONT COTTONWOOD. 



No tree is more common, more beautiful, nor more valuable as a 

 ii-hade tree than the cottonwood. It grows naturally on almost 

 every stream along the Boundary, and is planted around the houses 

 and along the irrigation " acequias " of nearly every ranch. In Cali-. 

 fornia it is less abundant than in Arizona, New Mexico, and Texas, 

 but was found on the Salton River " of the Colorado Desert, at Moun- 

 tain Spring, on the east side of the Coast Eange, and on Jamul 

 Creek, near the Pacific Ocean. 



The habit of the cottonwood, of course, varies according to en- 

 vironment. In deep, narrow canyons, where it reaches upward 

 toward the light, its stem is very tall and slender, as is also the case 

 where the tree growth is close and crowded along the streams; 

 but, in open spaces, trees growing singly have full round tops with 

 spreading or often drooping branches, affording grateful shade to 

 man and beast and a home to many species of birds. Probably the 

 largest cottonwoods grow on the upper course of the Yaqui River, 

 in Mexico, but these I have not seen. Respecting a very large cotton- 

 wood, seen in central Arizona by Dr. Paul Clendenin and myself, 

 I find the following record in my note book of 1 885 : 



When wo reached the Agua Fria we halted for a noon r^st hi a grove of 

 remarkably large cottonwoods. ^Ye measured the largest tree with a tape-line, 

 taking the measurement at a point 4 feet above the ground. It was 34 feet 

 in circumference and had no excrescences or morbid growths at that part, the 

 trunk being symmetrical and rather tall, although the branches, which are very 

 long and drooping, almost reach to the ground. 



The height of this tree — probably the largest I ever saw — was not 

 indicated in the notes. From memory I should judge it to be about 

 23 'meters (75 feet), though it may have been more. A very hand- 

 some cottonwood that was photographed at mA' request by the Com- 

 mission's photographer grew beside the Santa Cruz River, in Sonora, 

 at 4,300 feet (1,311 meters) altitude. It measured 16 feet (5 

 meters) in circumference arid 80 feet (24 meters) in height. (See 

 Plate VI, fig. 1.) 



The Cottonwood's vertical range is from near sea level (Jamul 

 Creek, California) to 6,100 feet (Huachuca Mountains, near Fort 

 Huachuca). 



The leaves are shed in autumn or early winter, and are again 

 assumed some time from February to April, the dates varying with 

 the altitude. Traveling from Fort Verde, in central Arizona, to 

 Phoenix, Arizona, in 1885, it was noted that but few cottonwoods in 



" Populus icislizpiii (Watson) Sargent is the species of the upper Rio Graude, 

 !> Dr. J. N. Rose considers the Salton River tree au undescribed species, 



