194 



UNIVERSITY OF COLORADO STUDIES 



broad; coarsely serrate or crenate with less than ten teeth on each side. Leaf- 

 stalks slender, nearly as long as the blades. 



A large spreading tree with stout, light-orange-colored glabrous branchlets. 

 Wood light, soft, used for fuel; specific gravity 0.4621. Bark pale gray-brown, 

 divided into broad, somewhat rounded ridges. 



Southern Colorado, south to Texas and Arizona; the common cottonwood of 

 the Rio Grande valley in western Texas and New Mexico. Reported by Rydberg 

 from Arboles, Grand Junction, and Colorado Springs in this state. 



5. Populus sargentii' Dode. Western Cottonwood 



Rydberg, Flora Colo. 91 (as P. occidentalis); Coulter, Manual 339 (as P. 

 angulata); Sargent, Manual Trees of N. .4. 164 (as P. deltoides, var. occidentalis); 

 Nelson, Key to Rocky Mountain Flora 15 (as P. deltoides). 



Leaf-blades broadly deltoid or heart-shaped, 

 about 8 cm. (3^ in.) broad, with narrow 

 acuminate points; dark green and shining 

 above, slightly paler beneath; toothed or serrate 

 except at base with more than ten teeth on each 

 side. Leaf-stalks laterally compressed in the 

 upper part, somewhat shorter than the blades. 

 A large or medium-sized tree, the trunk 

 generally divided about 5 meters above the 

 ground into several massive limbs which spread 

 rather widely and give rise to a wide, open 

 crown. Bark of young trees thin, becoming 

 on old trees thick and deeply divided into 

 broad, rounded ridges; that of younger trunks 

 and branches cream-gray or tan color, but dark 

 gray in old trees. Wood light, soft, not strong, 

 close grained; heart -wood brownish, sap-wood 

 nearly white. Used for fuel and in building 

 fences and sheds. Could be used for pulp manufacture. 



Rocky mountain region from Canada to Arizona and east to Kansas and Ne- 

 braska. This species grows on river bottoms of the plains region and in canyon 

 mouths but not at high altitudes. According to Rydberg's Flora it ranges (in Colo- 

 rado) from 4,000 to 7,000 feet but he reports a specimen collected near Eldora, 

 altitude 8,400 feet. There is very little difference between this species and Populus 



' The author is under obligation to Dr. P. A. Rydberg of New York for information in regard to the name 

 for the western cottonwood. According to Dr. Rydberg the name occidentalis is preoccupied by a fossil species. 

 Professor Dode of Paris has named a number of new species from garden material. Of these species P. 

 sargentii is our tree. Perhaps some of the others are mere forms of it. Since the other names appear first 

 on the page they have priority. So if they shall prove to be our tree the name sargentii will have to be dis- 

 carded and one of the other names used instead. These are: P. besseyana and P. henryana. 



