no 



THE SPIRIT OF THE SOIL 



When the variation in weight is plotted as before 

 against time in days, the effect of the Silver nitrate 

 extract which, it will be remembered, was added to 

 the extent of only about i part in 3,000,000, is 

 most remarkably emphasized. As before, the dotted 

 line represents the growth of the plants fed on pure 

 culture, the unbroken line that of the plants supplied 

 with Silver nitrate extract of treated peat. 



I 2fc 



~/\ 



3P 40 



10 20 



Time 



In view of the very slight increase of growth made 

 by the untreated plants, the assumption seems 

 justified that during germination certain substances 

 are developed which enable the embryo to utilize 

 the food material present in the seed, and that these 

 substances can be replaced in whole or in part by 

 the Silver fraction from an extract of bacterized 

 peat. 



