A RARE FORM OF ASPEN. 

 By J. S. Boyce. 



Aspen (Populus tremuloides Michx.) is not a common spe- 

 cies of the Southwest because there are only a few mountain 

 peaks or ranges which are high enough to cause favorable cli- 

 matic conditions. One of the best areas for a study of the 

 species in Arizona is to be found on the Coconino National 

 Forest which is located in the mountains of northern Arizona. 

 About the San Francisco peaks the aspen occurs on many slopes 

 at an elevation of 7600 to 8000 feet or higher in intimate mix- 

 ture with Western Yellow Pine (Pinus ponder osa Laws.). At 

 the lower altitude of 7000 to 7300 feet the species is usually 

 confined in detached clumps to the heads of small draws. 



The type form of aspen on the Coconino Forest has semi- 

 orbicular sometimes ovate leaves with very slightly pubescent 

 margins. The apex is abruptly narrowed into a short broad 

 point, slightly serrate with small incurved glandular teeth, while 

 the base is cordate-truncate, wavy in outline and without serra- 

 tion. The petioles are compressed laterally and are usually 

 greenish, rather heavily tinged with red. The leaves are a dark 

 green color on the upper side but are lighter on the lower side. 

 In the autumn they turn to a rich golden yellow, an orange red 

 or occasionally a russet brown and the last two colors are par- 

 ticularly noticeable on trees situated in the bottom of small can- 

 yons. The bark is prevailingly whitish and of a lighter shade 

 than is found in the Northeast. 



An undescribed type of aspen for this locality was found at 

 an altitude of 8600 feet, aneroid determination, covering about 

 an acre. The stand is located approximately an eighth of a mile 

 northeast of Campbell's Ranch along a trail leading up from the 

 house on the south slope of the San Francisco Peaks. The 

 site is a gentle slope with a southeast aspect where the soil is 

 six inches to two feet or more in depth, rich and composed of 

 fine particles with numerous large granitic boulders and many 

 small rocks. 



The trees occur in a few small clumps of pure stands gradual- 

 ly grading into the widely distributed prevailing type. Other 

 species in mixture are Western Yellow Pine, Limber Pine (Pinus 

 flexilis James), and Douglas Fir (Pseudotsuga taxifolia Britt.). 

 White Fir (Abies concolor Gord.) and Arizona Cork Fir (Abies 

 arizonica Merriam) are found at the same elevation but not in 

 mixture since none of these species occur in this immediate 



