The Twisting of Pines. 



Anstruther Davidson, C. M . , M . D . 



A few years ago when I made my first visit to the Bear 

 Valley district in the San Bernardino Mountains, I traveled 

 by stage on the old road by Squirrel Inn. This drive after 

 the erest of the ridge is attained, runs through continuous 

 forests of fir and pine and is an altogether delightful trip. 



Many dead still upright trees mostly denuded of their 

 bark are to be seen. Many of the dead trees show a spiral 

 twist in the grain. This twisting is very conspicuous, it 

 usually runs in this district from left to right, but quite a 

 number run from right to left. Of the stage driver, an intelli- 

 gent mountaineer I inquired what was the cause of this 

 peculiar phenomenon. "Well you see it is this way. All pines 

 are male or female; those with the twist in their composition 

 are the female." That observation suggested a better ac- 

 quaintance with humanity than with trees and left the ques- 

 tion still unsolved. 



This season in visiting Redondo I observed this spiral 

 twisting in actual operation and the cause of it in this instance 

 at least was simple enough. Very few trees in the West are 

 absolutely symmetrical in the development of their branches. 

 The branches on the south side or sunny side of the tree are 

 usually markedly better developed, with denser foliage. The 

 trade winds blowing steadily and strongly from the west all 

 summer bear greatest pressure on the larger and denser limbs, 

 so that the natural grain of the wood becomes twisted towards 

 that side on which the wind produces the greatest pressure. 

 When a number of trees grow closely in a group only those 

 on the outside show unilateral development and those twist 

 left or right according to the position of their heavier branches. 

 The illustration shows this process occurring in Eucalyptus 

 trees at Clifton, Redondo. This Eucalyptus being a fast grow- 

 ing tree and in a situation where the afternoon hreeze is 

 always strong shows it to an extreme degree. This twisting 

 of the grain of the wood is' probably limited to our evergreen 

 trees with dense obstructive foliage, such as pines and Euca- 

 lypti bear. The pines thus affected are not of much value 

 to the lumberman and it is to this fact that we owe the preser- 

 vation of some of the finest trees in our present reserves. As 

 one surveys the trees we cannot help noting that almost every 

 large pine or Douglas spruce displays a deep gash in the trunk. 

 That was produced by the shake splitting woodman to test 

 the grain of the wood. If the grain was twisted the tree was 

 no use for shakes, so it was allowed to remain and as the 

 straight grain trees were relatively few, we have preserved to 

 us many magnificent trees that otherwise would have long ago 

 been sacrificed. 



