2 Forms of Trees. [zor 
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 aresome 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 toa sheltered one. This is by 
