CLIMATIC FACTORS : THE AIR 103 



windward side of the trunk and increase proportionately on the 

 leeward side, thus forming a brace under the added top. An ex- 

 treme illustration is a section of trunk taken* from a Monterey 

 cypress that grew on Cypress Point, just south of Carmel Bay, 

 California. It is 74 inches in the diameter that grew parallel to the 

 prevailing wind but is only 9 inches in the opposite diameter. Only 

 50 growth rings were formed on the windward portion of the 

 section, but the leeward portion (71 in.) has 304 rings. This section 

 was taken 24 feet above the ground. 



Other physiological effects might be mentioned, but they are 

 largely brought about within the plants themselves through adap- 

 tations that serve to reduce the rate of transpiration through their 

 effects on stomata. In the drier sections of the country, such as the 

 plains and desert, the almost continuous dry winds increase tran- 

 spiration rates materially and serve to accentuate the effects of low 

 water supply. 



Physical Effects on Plants.— Most people have seen the effects of 

 a strong wind (25-38 miles per hour) upon vegetation. It is not 

 uncommon for dead branches to be torn from trees; an occasional 

 tree, especially if overmature and diseased, may be blown down. 



(—■■■■'■ 



FlG. 48. Asymmetric growth of a live oak (Quercus virginiana) exposed 

 to ocean wind and salt spray from the right. North Carolina coast.— U. S. 

 Forest Service. 



*Collected by and in the possession of W S. Cooper, University of Minne- 

 sota. 



