318 COlSTTRIBUTIOZsrS FROM THE NATIONAL HERBARIUM. 



1. Populus tremuloides Miclix. Aspen. Common at low altitudes, usually 

 forming dense pure stands. Alaska to Mex., Tenn., and Newf.— Slender small tree, 

 or often only a shrub; bark thin, smooth, whitish or pale green; leaves slender- 

 petioled, rounded, 2 to 5 cm. long, glabrous, pale green, finely toothed. 



Known also as quaking aspen and often locally as "quaking asp." The leaves 

 are often deformed by galls; in autumn they turn yellow. The aspen is very 

 abundant along the automobile road on the east side of the park, often in dense 

 stands, but it does not extend far up the slopes. In exposed places the plants are 

 shrubby and often prostrate, probably as a result of heavy snowfall. Aspens seem 

 to be absent about the head of Lake McDonald, but they are abundant about Belton. 

 According to the writer's experience — and his observations have been confirmed by 

 those of other persons — this tree is seldom found in fruit. If a cut is made in the 

 smooth bark a scar is formed which remains throughout the life of the tree, but in 

 Glacier Park visitors seem unaware of the possibility of leaving a permanent record 

 of their visit upon the aspen trunks, and verj^ few trees thus disfigured were noticed. 

 In New Mexico the writer has often marveled at the great number of trees upon 

 which people have cut their names or initials with dates and various designs. There, 

 even in the most remote places, often almost every tree is thus marked, until one 

 wonders if the whole population has conducted a concerted campaign for the purpose. 

 Trees are often found upon which the inscriptions are 30 years old or more. 



The aspen is one of the first trees to spring up on burned or cut-over areas, and it is 

 thus important in reforestation. The reason for its rapid appearance in such places 

 is, of course, the form of the seeds, which are scattered by the wind. The wide 

 dissemination of the tree perhaps indicates that seeds are borne in greater profusion 

 than casual observations would indicate. Aspen wood is useful for making paper. 



2. Populus trichocarpa Torr. & Gray. Black Cottonwood. Common on the east 

 slope, at low altitudes, usually along streams. Alaska to Calif, and Mont. — Large or 

 small tree; bark on young trees and on younger branches smooth and resembling 

 that of the aspen, on old trunks deeply furrowed, white, with a soft chalky appear- 

 ance, in old age sometimes blackish; leaves slender-petioled, broadly ovate to lance- 

 ovate, 6 to 12 cm. long (on sprouts often much larger), acute, finely toothed, green 

 on the upper surface, pale beneath, usually hairy when young but soon glabrous. 



3. Populus hastata Dode. Western balsam poplar. Common on the west 

 slope at low altitudes, along water or in woods. Idaho, Mont., and Alta. — ^Like 

 P. trichocarpa^ and differing only in the glabrous fruit. 



It seems rather doubtful whether this is a distinct species. The writer is unable 

 to give any information concerning the distribution and relative abundance of these 

 two species (if they are species) in the park. It was taken for granted that only one 

 species was represented until study of the collections in Washington revealed the 

 presence of two. When the writer \isited the park, the fruiting catkins had all 

 fallen, but they were found, of course, under the trees. With leaf specimens alone 

 it is impossible to determine which species is represented. Only two specimens of 

 fruit were secured; one from the east entrance is P. trichocarpa, and one from Lake 

 McDonald is P. hastata. Whether one species is confined to the east and one to the 

 west slope, or whether the two grow together, it is impossible to say without further 

 field study. 



The cottonwoods are usually associated with other trees, especially aspens, but 

 sometimes they form small pure stands. The trees on the west slope are often thickly 

 covered with lichens. Some trees have leaves almost as narrow as those of P. angusti- 

 folia, and the leaves of small seedlings appear to be narrow always. Cottonwoods 

 seem to have great vitaUty, and the writer noticed some logs that had been cut at 

 least a year before which were sending out sprouts. 



