118 L. COHEN. 



Water exists in the soil in two states, depending on 

 atmospheric conditions, namely, hygroscopic and capillary, 

 the term hygroscopic being applied to that condensed 

 aqueous vapour which is retained by the soil in a dry 

 atmosphere or absorbed by an artificially dried soil from 

 moist air, and adheres as a film to the soil particles, and 

 the term capillary to the water from rain, irrigation, or 

 upward capillary action from " bottom water" which fills 

 up more or less completely the interstices between the 

 particles. It has been shown by repeated experiments 

 that soil contains water-soluble salts to the extent, in the 

 poorer and richer soils respectively, of between about *02 

 and *05f, which from the method of determination may be 

 assumed to be in a state of solution in the water, hygro- 

 scopic or capillary, that the soil contains. Now the amount 

 of moisture varies, of course, to a very large extent in a 

 given soil, according as the weather conditions are rainy 

 or droughty, being sometimes as low (when hygroscopic 

 only) as 2'5i and as high as 40°/° or more when "wet," that 

 is, saturated with capillary moisture. 



Let us now consider the growth of a seed or young plant 

 placed in a nutrient aqueous solution, that is, pure water 

 in which have been dissolved the acids and bases in relative 

 proportions similar to those present in plant-ash, and we 

 find that normal results obtain only when the solution is 

 below a certain limit of concentration, and development 

 becomes more and more retarded as the solution becomes 

 stronger, until the limit of tolerance of that particular 

 plant is reached. Let us say that this occurs when the 

 water contains x°\» of salts. (The numerical value of the 

 symbol will depend on a variety of factors, such as nature 

 of plant, habit, preponderance of one salt over another, or 

 the presence of one, such as carbonate of soda, which exerts 

 an apparently toxic action on certain crops.) Considering 



