trees and the great number of dead branches in the crowns are 

 also characteristic features. 



A closer examination reveals another striking fact. The 

 trunks themselves in cross section have an ellipsoidal tendency 

 with the longer axis lying parallel to the direction of the pre- 

 vailing wind. The high development of bark and the small 

 diameter and great age are but other evidences of this same 

 factor. We thus see that a high and constant wind not only 

 defines the whole landscape but determines the individual plant 

 form as well. The modification of internal structure resulting 

 from the mechanical impact of the wind is evidenced in the great 

 increase of mechanical tissue; and it is to this increase that the 

 trunk owes its ellipsoidal form, mechanical tissue developing 

 only abnormally where the stimulus of the strain is focused, 

 obviously on the leeward side perpendicular to the wind impact. 



The influence of wind upon transpiration though not the most 

 evident is by far the most significant. Other things equal, the 

 rate of transpiration is dependent upon the difference in diffusion 

 tension of water vapor within and without the plant body. The 

 desiccating influence of a wind blast is well known and needs 

 but to be recalled in this connection. This desiccating effect, 

 along with the constant replacement of the atmospheric environ- 

 ment, reduces the external diffusion to a minimum, thus aug- 

 menting transpiration greatly beyond its normal amount. Fur- 

 thermore, during winter, the resting periods of plants, the wind 

 reaches its highest velocity (see Table III) thus keeping the 

 peaks and higher slopes bare a large part of the time and 

 reducing the available moisture in the soil to a minimum. Coin- 

 cident with this maximum wind velocity are the minima of pre- 

 cipitation and temperature. (See Tables II and V). It like- 

 wise dries the plant itself, even thawing the frozen sap, thereby 

 increasing the transpiration at a time when this excessive drain 

 can least well be met, concomitant as it is with a period when 

 absorption, because of the dryness of the soil and its low tempera- 

 ture, is highly impaired if not entirely prevented. We-have thus 

 a condition of excessive transpiration and diminished absorption. 

 In other words, the ratio of transpiration to absorption is at a 

 maximum. The existence of this high transpiration ratio 



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