OCT.. 1899.] 



WHITE-B.\RK PINE BELT. 



43 



tbem descend in tongues considerably below the nsual lower limit of 

 the belt to which they belong. The most extreme ease of the kind 

 observed is on the east side of the series of hills and ridges known on 

 the map as 'dray 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 7,1*00 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 



Fig. 25. — Group of alpine liemlocks 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 IJange. 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 (tig. 20) meas- 

 ured G feet. It is a characteristic habit of hemlocks on sloping ground 

 to grow in 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. 



