32 NORTH AMERICAN FAUNA. [No. 16. 
not the two actually intergrade, while an interesting question, is of 
little consequence compared with the fact that here, as in the Sierra, 
the two trees occupy adjoining but distinct belts—ponderosa the warmer 
and normally the lower; jeffreyi the colder and normally the higher. It 
sometimes happens, however, as in places along the cold east base of 
the Scott Mountains, where local conditions produce abnormal tempera- 
tures, that a strip of Jeffrey pine is sandwiched in between two areas 
of ponderosa pine. In this instance the low temperature comes in part 
from the cooling effects of cold streams, and in part from the afternoon 
shadows of the mountains. 
The ponderosa forest is nowhere pure over any large area, but is 
sprinkled in varying proportion with sugar pines, incense cedars, 
Douglas firs, and white firs, and at lower altitudes with black oaks. 
The stately sugar pines are so valuable for lumber that the best have 
been already cut, but enough remain to show that the species was 
formerly common in most 
parts of the ponderosa for- 
est. The incense cedars 
also are scattered over the 
wholeregion, but the Doug- 
las and white firs require 
more moisture and conse- 
quently are less evenly dis- 
| lee tributed. They are most 
: abundant on the borders 
a of streams, in cool canyons, 
and along the well-watered 
east base of Monnt Eddy and the Scott Mountains, where they become 
the dominant trees, the ponderosa pines being comparatively scarce. 
On drier and warmer soil, away from the cooling influence of the Scott 
Mountains, the ponderosa pines rapidly increase, and in the area 
between Black Butte, Shasta Valley, and the mountain, although 
sprinkled with incense cedars and black oaks, they form the purest 
ponderosa forest of the region. 
Another conifer of the yellow-piune belt is the knobcone pine (Pinus 
attenuata), va narrow interrupted tongue of which pushes up Panther 
Creek. The deciduous trees of this belt are the black oak (Quercus 
californica), Oregon maple (-lcer amacrophyllum), tree alder (Alnus 
tenuifolia), and Oregon dogwood (Cornus nuttalli), The maple and 
dogwood are restricted to the lowest levels and do not occur in very 
dry places; the alders are confined to the neighborhood of water; the 
oak ranges more widely over the lower half of the pine belt and thrives 
on dry as well as on moderately moist soils. 
The conifers will be considered as individual species. 
SuGaR PINE (Pinus lambertiana).—The sugar pine is the largest, 
handsomest, and noblest of our western pines, and its wood is so 
Fri. 16.—Cones of ponderosa and Jcttrey pines. 
