Sainpsoii and Allen : physical factors on transpiration. 53 



tops were removed by cutting just above the surface, the green 

 weight taken, and leaf areas obtained in the usual way. 



In the "Soil Type" series, dry weight and ash determinations 

 were made of the leaves. In the duplicates, however, measurements 

 were carried on as far as transpiration was concerned, but owing to 

 the great amount of work involved, the other measurements were 

 made for one series only and not for the duplicates. The results 

 on the experiment with soil textures are shown in the table which 

 follows : 



TABLE XI. 



Theke is no appreciacle difference in the size or vigor of 

 THE plants grown in the various textures, as is indicated by Fig. 

 8 and by the green weight shown in the table. The amount of 

 transpiration is greatest per unit area in the largest particles of 

 soil, there being a difference of about eighteen milligrams per square 

 centimeter in the two extreme types during the day, and about 

 twelve milligrams at night. 



The explanation for this phenomenon is that the physiological wa- 

 ter content of the soil with larger particles is greater than that 



