1917] Sargent,— Botanical Activities of Percival Lowell 23 
Arboretum, including that of an Oak which he had found growing 
near his observatory and which so far as it is possible to judge is an 
undescribed species. Interest in this Oak led him to look for other 
individuals and to extend his botanical explorations. During these 
he visited Oak Creek Canyon, a deep cut with precipitous sides in the 
Colorado plateau which heads about twenty miles south of Flagstaff 
and carries in its bottom a small stream which finally finds its way into 
the Verde northwest and not far from Camp Verde. Lowell appears 
to have been the first botanist who visited the upper part, at least, 
of this Canyon where he found a number of interesting plants, notably 
Platanus Wrightii and Quercus arizonica, which before his explorations 
were not known to extend into the United States from Mexico beyond 
the canyons of the mountain ranges of southern Arizona and New 
Mexico. In Oak Creek Canyon Lowell found a new Ash-tree some- 
what intermediate between Fraxinus quadrangulata of the east and 
F. anomala of our southwestern deserts which will bear his name. 
Later Lowell explored Sycamore Canyon which is west of Oak Creek 
Canyon and larger and deeper than Oak Creek Canyon and, like it 
cuts through the Colorado plateau and finally reaches the Verde near 
the mouth of Oak Creek. 
Juniperus in several species abounds on the Colorado plateau, and 
Lowell became deeply interested in these trees and was preparing to 
write a monograph of our southwestern species. His observations 
on the characters and altitudinal range of the different species, illus- 
trated by abundant material, have been of great service to me. 
Lowell’s only botanica? paper, published in the May and June issues 
of the Bulletin of the American Geographic Society in 1909, is entitled 
“The Plateau of the San Francisco Peaks in its Effect on Tree Life.” 
In this paper, which is illustrated by photographs made by the author 
of all the important trees of the region, he discusses the altitudinal 
distribution of these trees, dividing his region into five zones which ` 
he illustrates by a number of charts showing the distribution of vege- 
tation in each. It contains, too, an important and interesting dis- 
cussion of the influence on temperature and therefore on tree growth 
of the larger body of earth in a plateau as compared with a mountain 
peak where, on account of greater exposure, the earth cools more 
rapidly. 
A bundle of cuttings of what is probably a new species of Willow, 
to obtain which Lowell had made a long and hard journey, with his 
