(b) Wind. The influence of wind upon vegetation is great 

 and manifests itself in a variety of effects. Indirectly, plant life 

 is influenced by the wind in furthering dissemination and facili- 

 tating anemophilous pollination. While more directly the 

 external form, internal structure, and vital processes may be 

 greatly modified and disturbed by the mechanical impact on the 

 one hand and the desiccating effects concomitant with high wind 

 velocity and extreme exposure on the other. The extent of these 

 influences is largely dependent upon two conditions; the plant's 

 exposure and the strength and prevalence of the wind. These 

 two conditions exist in a superlative degree upon mountains and 

 are proportionally great as the altitude increases. As the action 

 of wind induces a complex of consequences in plants, it will be 

 well to discuss the various effects independently. 



The study of seed dispersal has two aspects : the pure ecologi- 

 cal standpoint dealing with varied adaptive structures facilitating 

 seed dissemination, and the floristic phases treating of questions 

 of origin and present distribution. The large per cent (about 

 30%) of the flora possessed of adaptations furthering wind dis- 

 persal is at least deserving of passing notice. 



Wind is a factor not to be underestimated in its relation to 

 pollination. Though many insects abound even to the summit 

 they are presumably of little significance in entomophilous polli- 

 nation, belonging as they do to groups whose members aid only 

 slightly if at all in pollen transportation. Further, the majority 

 of forms are strongly anemophilous. The great efficiency of 

 the wind in the formation, as well as the dispersal, of seed is to 

 be properly accorded in the consideration of any alpine flora. 



The most evident wind effect upon plants is the modification 

 of morphological form. Though formerly controverted, it now 

 seems well established that this influence is partly mechanical 

 and largely due to the force of impact of the wind blast. It 

 directly follows that the extent of this modification varies with 

 exposure and the velocity and constancy of the wind. We may 

 expect to find then upon Ktaadn drastic evidence of wind influ- 

 ence upon external form. As one ascends the slopes he passes 

 successively from forest trees which clothe the plain below 

 through those whose branches just overtop his head, those that 



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