28 STUDIES IN THE VEGETATION OF THE STATE 



Per Cent of Water Loss m Plants and Soils. 



The table above is not accurate as to the time of drying 

 out given for sand, or as to its water loss, because the plants 

 in sand were watered in order to keep them alive until they 

 would die under the same temperature conditions as those 

 in the other soils. 



The great difference which these results show in the com- 

 parative amounts of water in the soil and in the plant at the 

 time of wilting call for an explanation which at the best 

 must be more or less theoretical. We may assume that the 

 difference of 8 per cent, between the sand and the clay is due 

 solely to a difference in capillarity and surface tension, and 

 to the presence of a greater amount of hygroscopic water in 

 the clay. This explanation may account for the greater 

 portion of the difference between clay and sand. It will not 

 however explain why the plant wilts at a higher per cent, 

 of soil water in loam, humus and saline soils. 



The sand used was quartz sand and contained only 

 a trace of soluble salts. On the other hand, the saline 

 soil had the highest per cent, of soluble matter. May 

 it not be possible that the concentration of these salts 

 as the soil gradually loses water is a factor that plays a very 

 important part in checking the interchange which takes 

 place between the solutions in the protoplasm of the root 

 hairs, and the soil solution? There is no doubt that the in- 

 creasing capillarity and hygroscopicity of the finer soils 

 impedes this important process, either causing it to cease, 

 or bringing about an actual transfer of solutions from the 

 protoplasm of the plant to the soil solution. In the case of 



