40 



SCIENTIFIC REPORTS OF THE AGRICULTURAL RESEARCH 



author to support the view that the roots of crop plants 

 excrete toxic substances. It may, however, be noted that 

 these experiments ^were performed with ordinary well 

 water and without any control tests, and that the method 

 of experiment led to a considerable evaporation of water 

 and a corresponding concentration of the dissolved salts. 

 This being the case it was felt that the evidence was not 

 conclusive and that a repetition of the experiments under 

 more stringent conditions was desirable. With this ob- 

 ject in view the same scheme of experiment was repeated 

 with the exception that a synthetic nutrient solution was 

 substituted for the well* water, and " control tests " were* 

 introduced to check the results. The nutrient solution used 

 was that of Knop. 



A large number of wheat, rahar and gram seedlings- 

 were grown in this nutrient solution, and at the end of a 

 certain period the solution was allowed to evaporate spon- 

 taneously until its volume was reduced to about one-eighth. 

 The blanks were allowed to evaporate to one-third to one- 

 fourth the original volume. Jars containing nutrient 

 solution but bearing no seedlings were also treated in an 

 identical manner, and constituted. the "blanks." Seedlings 

 were then introduced into these concentrated solutions,, 

 supposed to contain the excretions of plant roots, and the 

 progress of crops grown in them was recorded. The 

 results are noted below : — 



