10 Hall, Hmv does the Plan! obtain its nutriment ? 



The next stajje in the investigation was to asceitaiti 

 how far the concentration of tlie nutrient solution had an 

 effect upon the growth of the plant. A standard solution 

 was made up and diluted to 1, -iVj ^^tcI ^V respectively, 

 barley being again the plant selected for growth. From 

 the very outset growth proceeded in the order of the 

 concentration of the solutions, but the results might be 

 open to the objection that the solutions became exhausted 

 and the final state of the plants had been limited b}"- the 

 amount of food at the plants' disposal. 



Another series was then arranged on the same lines, 

 except that the solutions were renewed weekl}-, so as to 

 secure that the plant always had some nutriment at its 

 disposal. 



The photographs {PL /., Figs, i & 2) representing early 

 and late stages in the development of these plants, 

 sufficiently indicate that the rate of growth depended 

 directly upon the concentrations of the solutions and not 

 merely upon the amount of food available for the plant. 



Two further series of trials were then carried out, in 

 which the plants were grown in coarse sand contained in 

 vertical glass cylinders, through which the nutritive 

 solution of var}'ing concentrations was allowed to percolate 

 slowly, so that the roots were alwa}'s in contact with a 

 constantly renewed solution of the concentration indicated. 

 Again, the photographs, PI. 11. , may be taken as sufficient 

 indication of the character of the results obtained, which 

 confirmed the conclusion that within certain wide limits 

 the concentration of the nutritive solution is a factor in 

 the rate of plant growth, irrespective of the total amount 

 of plant food available. 



The main purpose of the investigation had now 

 indeed been attained. Actual soil solutions made from 

 known soils had been found to vary in composition in 



