504 Prof. W. B. Bottomley. Effects of Auximones on 



agency of aerobic bacteria under suitable conditions. Hence the active 

 growth-promoting substances obtained in solution from this must be 

 products of decomposition of organic matter. Further experiments, not 

 yet published, have shown that these substances are also obtainable, in 

 relatively small amounts, from well-rotted stable manure and thoroughly 

 decomposed leaf-mould. It is to be expected, therefore, that small quantities 

 would be formed among the products of organic decay in ths water of a 

 pond, and it is interesting to note, in this connection, that in nature Zemna 

 plants flourish best in stagnant water, rich in organic decomposition 

 products. 



Until more is known as to the nature of these products, it is impossible to 

 state definitely how they function. Some of them may be absorbed and 

 utilised directly as plant nutrients. Schreiner and Skinner* have shown 

 that such nitrogenous decomposition products as creatinine, histidine and 

 arginine can replace nitrates in a culture solution, and that, even when 

 nitrates are present, these substances are absorbed by the plants. They say 

 that " these compounds are absorbed as such, and utilised directly for 

 building up the proteins and other complex nitrogenous constituents of 

 vegetable material." They also suggest that the energy usually employed 

 in a plant in effecting the chemical transformation of inorganic nitrogen 

 into an organic form can be expended otherwise when these substances are 

 supplied to the plant, and thus " plant efficiency is increased and growth 

 augmented when the plant obtains compounds which will serve directly as 

 tissue builders." 



On the other hand, some may have a similar effect to that of the accessory 

 food bodies or growth vitamines concerned in animal growth. The phospho- 

 tungstic fraction of bacterised peat was obtained by precisely the same 

 method as that used for extracting animal growth vitamines, and it is 

 difficult to understand how the addition of such a small amount of organic 

 matter as 13 parts per million from this material to a culture solution 

 already containing 5500 parts per million of mineral nutrient salts could 

 produce the results obtained if it represented only a further addition of 

 plant nutrient. The possibility that such accessory food bodies are present 

 in bacterised peat is emphasised by the fact that the water extract free 

 from humic acid, the alcoholic extract, and the phosphotungstic fraction, 

 have all been found to give a positive reaction with the Folin-Macullum 

 phosphotungstic acid reagent. This positive reaction, which is not given by 

 the corresponding fractions of raw peat, is considered by Williams and 



* Schreiner and Skinner, U.S. Dept. Agric, Bureau of Soils, Bull. 87, 1912. 



