848 EXPERIMENT STATION RECORD. 



Physiological chemistry. — A question of great importance in pliysi- 

 ology is tlie origin of the nitrogenous principles of plants.. The oxida- 

 tion of organic matter, especially nitrification, is an important subject 

 for investigation. 



Dehoraiu and Demoussy^ have continued their investigations upon 

 the maximum activity of ferments under the combined influence of 

 heat and humidity. In vegetable mold this maximum was reached 

 with a water content of 17 i^er cent and a temperature ranging from 

 22 to 44° C. and in garden soil with 25 per cent water and 22° C. At 

 44° the activity of the bacteria was checked, providing the water content 

 of the soil remained constant at from 17 to 25 per cent. 



Marcille,^ in his investigations on nitrification, found, as had already 

 been shown by Winogradsky, that the activity of the ferments A^aried 

 in different soils. In studying the comparative nitrification of phos- 

 phate and sulphate of ammonia he found that the phosphate was no 

 more favorable to the action of the nitrous ferment than the sulphate, 

 but that it did seem to favor the transformation of nitrites into 

 nitrates. BreaP has investigated the decomposition of vegetable mat- 

 ter in the presence of water and soil. He made a study of vegetable 

 infusions found in soils rich in organic remains. Water in contact 

 with decaying v^egetation becomes crowded with bacteria, which attack 

 the vegetable matter and produce ammonia. The excess of ammonia 

 checks the activity of the microih'ganisms. In no case did the organ- 

 isms produce more than 0.2 gm. of ammoniacal nitrogen per liter in the 

 infusions. When an infusion containing these organisms is incorpo- 

 rated in a lump of soil the ammonia is transformed into nitric acid at 

 the surface, while ammonia accumulates at the center, since the organ- 

 ism is incapable of activity in the absence of air. There is also a 

 reduction of the nitric acid produced. A soil which has already nitri- 

 fied the ammonia in an infusion with Avhich it has been watered is, on 

 that account, more able to nitrify more ammonia, the activity of the 

 nitric ferment seeming thus to be accelerated. Humus, Avhich is insol- 

 uble in water, dissolves in these infusions on account of the ammonia 

 secreted. The insolubility was restored by the introduction into the 

 infusion of the nitric ferment contained in the soil. 



Less ammonia and more nitrate are found in a soil that has been 

 mixed with vegetable debris than in the same soil if the litter is sim- 

 ply spread upon the surface. When the ammonia in these infusions 

 becomes sufficiently strong to kill the organisms producing it fungi 

 develop on the surface and transform the ammonia into nitrogenous 

 organic compounds. In meadows, peat beds, and in vegetable debris 

 which accumulates in humid soils the nitric ferment is not present, but 

 lungi of various kinds abound. Ammonia is taken up by the fungi 



1 Ann. Agron., 22 (1896), p. 305. 

 nbid., p. 337 (E. S. R., S, p. 569). 

 Hbid., p. 362 (E. S. R., 8, p. 479). 



