88 THE SOII, SOLUTION 



soluble organic substances which are toxic to plant growth yield 

 oxidation products which are harmless or positively beneficial. 



The suggestion has been made that the well-known infertility 

 of subsoils, when freshly turned up, is caused by the presence 

 of alkaloids of the purine or codeine type, due to the activities 

 of anaerobic bacteria. Water cultures and pot cultures show 

 that while these substances do have a marked effect on plant 

 growth, it is, frequently, quite beneficial ; strychnine for example, 

 in certain concentrations, produces a very decided stimulation in 

 the growth of wheat seedlings. It is clear that some other ex- 

 planation will have to be sought for the lack of fertility of sub- 

 soils. 



A number of the substances which may be expected for one 

 reason or another to be present in soils, have been investigated as 

 to their effect on plants. In this connection may be cited the 

 work of Livingston 1 and of Dachnowski, 2 who have studied the 

 effect on vegetation of the organic substances dissolved in bog 

 waters. In the following table are given the results obtained 

 by growing wheat seedlings in solutions containing some one of 

 a number of substances which might be expected to occur in a 

 soil or to be derivatives of such substances. It will be observed 

 that in the case of these dissolved organic substances, as has 

 been repeatedly established with the inorganic ones, in concentra- 

 tions sufficiently dilute not to be toxic, they generally show 

 the opposite effect and appear to be stimulating. 



1 Physiological Properties of Bog Water, by B. E. Livingston, Bot. 

 gaz., 39, 348-355 (iQOS). 



2 The toxic property of bog water and bog soil, by Alfred Dachnow- 

 ski, Bot. gaz., 46, 130-143 (1908). 



