462 



BOTAXICAL GAZETTE 



[juxe 



the foredune. All of these causes tend to exclude any but the 

 most hardy species, and even these are never abundant. The 



Fig. 2. — Average of mean daily evaporation rates in the 4 associations for grow- 

 ing seasons iqio, 1911, 1912. 



struggle with other plants is not important, since there are always 

 many unoccupied places, and the supply of available moisture is 

 plentiful. 



