84 THE SOIL SOLUTION 



tract, and especially if the extract so treated were allowed to 

 stand for a few days with free access of air, there was obtained 

 a culture medium which yielded remarkably good results with 

 wheat seedlings. Not only was there an excellent and increased 

 development of tops, but the roots of the seedlings grown in the 

 solution treated with pyrogallol were unusually long, turgid, 

 clear and translucent. Here, then, there was obtained an in- 

 creased amount and improved character of growth by the addi- 

 tion of a substance which contained only carbon, hydrogen and 

 oxygen, and no recognized plant food. Other organic substances, 

 such for instance as tannin, gave similar results. 



With the recognition that the presence of organic dissolved 

 substances in the nutrient medium produced effects on a grow- 

 ing plant of as great or even greater magnitude than those pro- 

 duced by inorganic dissolved substances, there was carried out a 

 number of experiments to test more specifically such substances 

 as might reasonably be expected to be present naturally in soils. 

 The results thus obtained suggested experiments with other re- 

 lated substances. The first substance to suggest itself is stable 

 manure. Taking it all in all, this substance is probably the most 

 efficient as well as the most generally used soil amendment in 

 the experience of mankind. The good effects produced by this 

 substance have in the past been generally considered as due to 

 the readily "available" potash, phosphoric acid and nitrogen it 

 contains, but thoughtful experimenters and agriculturists have 

 long doubted that this explanation is sufficient, since, after all 

 the mineral constituents of stable manure are usually small in 

 amount, and out of all proportion to the effects resulting from 

 its use. That some of the results are due to an improvement in 

 the physical condition of the soil when manure is used has quite 

 rightly been generally assumed ; but to its content of nitrogenous 

 components its value has in the main been ascribed. 



A well-fermented aqueous extract of stable manure was pre- 

 pared, and filtered free of suspended solids. Four equal vol- 

 umes of this solution were taken. Three of these portions were 

 evaporated to dryness in platinum dishes, and the residues 



