LEAP AND STEM STEUCTUKE OF THE OLIVE. 53 



To summarize: The leaf and stem structure of the ohve are such 

 as to protect it admirably against excessive loss of water by trans- 

 piration and hence adapt it to growing in very dry soils and climates. 

 The scanty evidence here presented would seem to indicate that the 

 considerable difference in aridity represented by the two environ- 

 ments at Niles (where the average yearly rainfall is 14.8 inches, where 

 moisture-laden winds blow in from the ocean, and where occasional 

 irrigation is given) and of Palm Springs (where the average yearly 

 rainfall is only 3.5 inches, where the air is excessively dry, and where 

 the trees had received no irrigation for seven years) has a distinct, 

 though comparatively slight, effect upon the anatomical structure 

 of this plant, for even at Niles the olive exhibits in a high degree the 

 characteristics of a xerophytic plant. 



192 



