ocr., 1899.] WHITE-BARK PINE BELT. 43 
them descend in tongues considerably below the usual lower limit of 
the belt to which they belong. The most extreme case of the kind 
observed is on the east side of the series of hills and ridges known on 
the map as ‘Gray Butte,’ where a gulch, sheltered from the warm after- 
noon sun and moistened by seepage from melting snows, carries the 
hemlocks to a lower altitude than they reach elsewhere. On suitable 
slopes they usually begin about 1,200 or 7,300 feet and range up to 
about 8,000 feet. The highest altitude at which they were observed is 
8,700 feet, a little east of Mud Creek Canyon, where a few stunted trees 
were found among the white-bark pines. Their extreme upper limit is 
thus a thousand feet lower than that of the white-bark pines. This is 
Fic. 25.—Group of alpine hemlocks near Deer Canyon. 
due, in part at least, to the character of the upper slopes, where no 
trees can grow except on the ridges—as explained under the head of 
Timberline (pp. 27-30)—and here the ridges are too exposed and too 
dry for hemlocks. , 
On Shasta the alpine hemlock does not grow in such luxuriance 
or attain such dimensions as in the Cascade Range. The average 
height of mature trees seems to be 80 or 100 feet; the average diameter 
a little less than 3 feet. Trunks 4 and 5 feet through are by no means 
rare and the one shown in the accompanying photograph (fig. 26) meas- 
ured 6 feet. It is a characteristic habit of hemlocks on sloping ground 
to growin clusters, 3 to 7 springing from a common base. In this way, 
when young, they are better able to withstand the pressure of the snow. 
