STEM AND LEAF STRUCTURE OF ASPEN AT DIFFERENT ALTITUDES IN COLORADO

Abstract

In this paper, the writer will attempt to point out the anatomical differences and similarities found in the trembling aspen (Populus tremuloides Michx.) collected at elevations of 5,800 feet and 9,ooo feet respectively. Gregory Canyon, near the city of Boulder, Colorado, marks the loweraltitude collection, and the town of Tolland, in Gilpin County, Colorado, and i8 miles from Boulder, the higher collection place. Although these two localities do not represent the lower and upper distribution limits of the trembling aspen, they approximate these limits closely, and, furthermore, offer a city and a town as definite geographic locations near which the collections were made. In making collections from the two stations, an attempt was made to gather material growing in similar situations. Exposed trees from io to 15 feet high on slopes facing the south were chosen. These trees were in both cases about fifty feet from a stream or stream bed, and on a slope sufficient to insure adequate drainage. Two collections were made from each locality; one in the spring, as the buds were swelling, and one in early autumn, after summer growth was completed. The spring collection from Gregory Canyon was made May 15, 1924. Spring was a little more advanced here at an altitude of 5,8o0 feet on this date than at Tolland with an altitude of 9,ooo feet on June 5; that is, spring at Tolland was just about one month later than in Gregory Canyon. The autumn collection was made at Tolland September 25, and in Gregory Canyon October I5. LEAVES AND BUD SCALES