38 



WATER-RELATION BETWEEN PLANT AND SOIL. 



series; otherwise a more pronounced lag behind evaporation would 

 have been here exhibited. The later graph falls more rapidly than the 

 earlier one, however, which suggests, as in the case of Coleus, that 

 incipient drying was more pronounced in the second series. The lower 

 maximum for the second series may denote lower transpiring power, 

 perhaps partly due to hardening, etc., of the older leaves and partly 

 to incipient drying and actual wilting, which occurred with hours 12 

 to 16, as shown in table 2. 



10 II 12 13 14 I5'l6'l7'ia'l9'20'2l'22'23'24' l'2'3 4'5'6'78'9 ' 

 Fia. 2. — Graphs for Vicia. 



