52 



STUDIES IN THE VEGETATION OF THE STATE 



which coincided approximately with the per cent of the non- 

 available water in each soil. The following are the ratios: 



The amount of soluble salts in the sand was so low that 

 the chemist did not determine it. It was very low, 

 posssibly not much greater than that of the tap water used 

 in watering the plants growing in it. This being the case 

 the same rule would hold as for the other soils, viz., the per 

 cent of non-available water in the soils increased as the square 

 root of the per cent of the soluble salts. Since the per cent of 

 soluble salts in the soil increases directly as the per cent 

 of water in the soil decreases, the increasing density of the 

 soil solution would tend to reduce the amount of available 

 food for the plant, and since the supply of watery foods for 

 it varies with difference in density existing between the sol- 

 utions in the protoplasm of the root-hairs and that of those 

 in the soil the protoplasm would take less water from the soil 

 solution just at the time the plant needed a greater water 

 supply. The fact that evaporation from the plant is aiways 

 excessive in times of drought would hasten the result. On 

 the other hand the rapid evaporation from the leaves, when 

 a plant is losing more water than it is getting would tend to 

 concentrate the solutions in the plant and increase their os- 

 motic efficiency in taking in water from the soil solutions. 

 These questions are of great interest and importance and 

 should be investigated thoroughly with reference to the plant 

 in its relation to the soil. 



The observations made in the field during August 1900, 

 brought out a fact of considerable importance, viz., that her- 

 baceous plants growing in hard soils could not root as deeply 

 as those growing in loose soils. Plants are enabled to grow 

 rapidly only when they can develop large and vigorous root 



