BOTANY OF LARIMER COUNTY 123 
than three or four inches per annum. Winters are cold and summers 
hot. There is a great daily range of temperature. At Ft. Collins the 
average annual temperature is 46.7 degrees Fahrenheit. Extremely 
low temperatures, as low as — 20 degrees occur a few times each winter. 
There is a great deal of wind and this comes chiefly from the west and 
‘northwest as is seen by the bent and twisted tops of the pine trees on the 
ridges and foothills. 
Floras of the Granite and Sedimentary Areas.—Since these two 
areas are in contact and extend for long distances at about the same 
altitude it is natural that they should have about the same species of 
plants. The pines (Pinus scopulorum) and cedars (Sabina scopulorum) 
are the only trees except in the gulches and on steep north slopes. Owing 
to the extremes of temperature and the slight rainfall together with the 
scarcity of soil, the formations are open. No close growth of pine was 
seen and the cedars are everywhere widely scattered, for the most part 
placed on exposed rocks at the tops of abrupt slopes. The most striking 
difference in the vegetation of the two areas is seen in the presence of a 
dense scrub of Cercocarpus over most of the sandstone and its almost 
entire absence on the granite. Lichens, though everywhere present on 
the granites are not at all common on the sandstone, and Selaginella 
also seems confined to the granite area. It is quite likely that Selaginella 
gets over on to the sedimentary rocks in places in this district, for it is 
abundant on rocks of the same geological formation at Boulder less than 
one hundred miles south. 
Owl Canyon and Vicinity.—Owl Canyon is a steep-walled gorge 
about a half-mile long cut through the lower members of the sedimentary 
series, which here dip to the east at an angle of about 15 degrees. The 
south wall of the canyon, being well shaded, affords an opportunity for 
the growth of a large number of species of shade plants, while the north 
wall, exposed to the hot sun, has a typical dry-ridge flora. A continua- 
tion of this latter formation is found on top of the ridge where conditions 
of extreme dryness exist due to lack of soil, exposure to wind and extreme 
insolation. Owl Canyon and vicinity were frequently visited by Pro- 
fessor C. S. Crandall, who was for a long time botanist of the Colorado 
Agricultural College, at Ft. Collins. A considerable number of species 
