2 Forms of Trees. [zoe 



If we again follow the vegetation further down to the plains, the 

 change in form is yet more pronounced. The trees are here as a 

 rule branched close to the ground, their crowns are wider and spread- 

 ing, the branches drooping and often sweeping the ground. The 

 general form, which in the higher Sierras was that of an elongated 

 pyramid, has here changed and become globular. We may call these 

 respectively, the spruce form, and the oak form. In the higher 

 mountains we rarely meet with the oak form, at least not in ever- 

 green trees, and on the plains the spruce form is equally rare. 

 There are some exceptions to this rule, but they are few and in no 

 way interfere with the theory which I will here set forth and en- 

 deavor to prove. Before we dwell upon the causes which have 

 been and yet are operating in creating and maintaining these char- 

 acteristic forms of trees, it is necessary to first consider those causes 

 which combine in affecting a change in the form of trees generally. 



Nearly every visitor to the wind-beaten and open seashore has 

 noticed the characteristic forms of trees and shrubs growing there. 

 The shrubs spread close to the ground, the trees lean towards the 

 interior, their crowns spread out horizontally and their branches are 

 thorny and knotty and continually bent. Such a sight is common 

 everywhere in exposed places. In sheltered localities inland these 

 same varieties grow upright, their crowns become less horizontal, 

 the branches less twisted, and the same shrubs, which on the sea 

 shore hug the soil, grow here straight and send out slender branches. 

 Even to the least observant the force that operates here and causes 

 the trees and shrubs to so change their shapes is the wind. When 

 we see such trees and shrubs painted on a canvas, we know at once 

 that the landscape is a wind-beaten one, and that the vegetation is 

 struggling against a force which is trying to destroy its foothold. 



But while the wind is especially active on the seashore in chang- 

 ing the natural or perhaps the original form of the trees and shrubs, 

 it is similarly effective to a lesser degree in any locality at all ex- 

 posed to winds. The interior plains, the cliffs on the sides of the 

 desert, the high mountain peaks, the elevated plateaus, the table 

 mountains, the slopes of the more sheltered sides of islands, in fact 

 everywhere may the power of the wind be perceived. 



The effects of the wind may be temporary or permanent; tem- 

 porary, if the plant regains its original form and outward appearance 

 when removed from the windy region to a sheltered one. This is by 



