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Volume 11 r>V'*A««><^y Number 1 



The Plant World 



JANUARY, 1908 



EVAPORATION AND PLANT HABITATS. 

 By. Dr. Burton Edward Livingston. 



In a previous paper* attention has been called to the 

 fact that, since the evaporating power of the air to a great 

 extent controls the rate of water loss from plants, this climatic 

 factor plays a prime role in inhibiting the growth of many 

 forms in arid regions. It was shown that a number of plants 

 fail to develop normally during the dry season at Tucson, 

 Arizona, although the soil in which they are rooted is kept 

 approximately at its optimum water content. The purpose 

 of the present paper is to call attention to the fact that the 

 evaporating power of the air also appears to play an import- 

 ant part in the determination of the vegetation which can 

 best succeed in different but neighboring habitats in the same 

 region. 



The amount of moisture present in the soil is controlled, 

 excepting in these comparatively restricted areas where the 

 subterranean water table is relatively near the surface, by 

 the relation between rainfall and evaporation, and it is doubt- 

 less partly through this indirect influence of the latter ele- 

 ment, as well as through the direct action of evaporation 

 upon the plant, that this relation is so satisfactory as a differ- 

 entiator between great centers of plant distribution.** Where 



•Livingston, B. E., Evaporation and plant development. The Plant 

 World, 10: 269-276, December, 1907. 



**On this subject the reader is referred to Transeau, B. N., Climatic 

 centers and centers of plant distribution. Ann. Report Mich. Acad, Scl. 7: 

 73-75, 1905. Idem, Forest centers of Eastern America. Am. Nat., 39: 875-889, 

 1905. 



