1914] 



FULLER— EVAPORATION AND SOIL MOISTURE 



217 



humidity 



from 



ma 



Fig. 14. — Diagram showing the comparative average da 

 different associations for the seasons of 1910, 1911, and 1912. 



poration rates in 



Cottonwood dune 

 Pine dune 



Oak dune 



Oak-hickory forest 

 Beech-maple forest 

 Edaphic prairie 



Fig. 



—Diagram showing the comparative mean average daily evaporation 



rates in the different associations for the three seasons investigated. 



II. Soil moisture 



The direct source of the water supply of plants being the mois- 

 ture in the soil, the amount of this moisture is evidently of the 

 highest importance to vegetation. This has been recognized by 

 many leading ecologists and phytogeographers. but very few data 

 have been made available as to the effects of definite quantitative 



