1908] Grinnell—Biota of the San Bernardino Mountains. 31 
Pinus ponderosa Douglas. 
The yellow pine was one of the commonest and most wide- 
spread trees of the region, on both the Pacific and desert slopes, 
marking well the Transition zone. I saw it as high as 9000 feet 
altitude on south-facing slopes such as the south face of Sugar- 
loaf, and near Dry lake, and on north slopes down as low as 5000 
feet. An example on the South Fork of the Santa Ana, near its 
mouth, was 218 feet in height (average of three tests). The 
tallest trees elsewhere measured were 175 feet in height or less. 
(See pls. 38, 17, 18.) 
Pinus Jeffreyi Murray. 
The Jeffrey or black pine occurred often with the last and 
seemed to hybridize with it freely ; at least intermediate examples 
were often noted. Tracts composed exclusively of the form 
Jeffrey’ were common along the upper Santa Ana, marking the 
Transition zone. Trees which bore cones heavily in 1906 were 
entirely barren in 1907. (See pl. 12.) 
Pinus Lambertiana Douglas. 
Sugar pines always occurred intermixed with other conifers, 
and in the Transition zone in its upper portion. It was numer- 
ous along the north base of San Bernardino peak, 6000 to 7800 
feet altitude, along the south side of the Santa Ana in many 
places, in the neighborhood of Bluff lake and between there and 
Bear lake, and more sparingly on the north slope of Sugarloaf 
up to 8000 feet. 
Pinus monophylla Torrey & Fremont. 
The pinon I should call a strictly arid Upper Sonoran spe- 
cies. It occupied a broad belt on the desert slope of the moun- 
tains, from 5000 feet altitude up over the ridges on that side to 
as high as 8000 feet, especially to the eastward of Sugarloaf. A 
tract extended down the north (south-facing) slope of the upper 
Santa Ana across the south face of Sugarloaf, at least down to 
5700 feet altitude. And I saw quite a number of pifons as low 
down on the Pacific side as 4600 feet in the brush belt on the 
sides of the Santa Ana, two or three miles below Seven Oaks. 
(See pl. 23.) 
