SOIL ORGANISMS 411 



reetly by plants without further change. Carbon dioxide and 

 water are formed continuously as the process advances. The 

 sulfur of the proteid compounds produces hydrogen sulfide 

 or free sulfur and later sulfates. 



Hutchinson and Miller,^ as well as other investigators, 

 have studied the question of the assimilation of nitrogenous 

 organic compounds by higher plants. The general conclu- 

 sions indicate that such a source of nitrogen is qiiite impor- 

 tant and sometimes allows the plant to benefit markedly from 

 the assimilation of such materials. Maize, for example, seems 

 to be particularly stimulated by farm manure, which carries 

 large amounts of organic nitrogenous compounds such as 

 urea. Acetamide, urea, barbituric acid, creatinine, alloxan, 

 peptone, and a number of other organic compounds have 

 been shown to be available to certain higher plants. 



Decay and putrefaction are carried on by a large number 

 of organisms, the higher fungi as well as such bacteria as 

 B, sultilis, B, mycoiSes, and similar micro-organisms engag- 

 ing in the decomposition processes. Some of the charac- 

 teristic, although not constant, products formed in the pu- 

 trefaction of albumin and proteins are albumoses, peptones, 

 and amino acids, followed by the formation of cadaverine, 

 putrescine, skatol, and indol. Where an abundant supply 

 of oxygen is present, or where a sujSieient supply of carbo- 

 hydrates exists, the latter substances are not formed. There 

 are many other products of putrefaction, including a num- 

 ber of gases, as carbon dioxide, hydrogen sulfide, marsh gas, 

 phosphine, hydrogen, nitrogen, and the like. 



Present-day knowledge of the subject does not make it pos- 

 sible to present a list of the organisms concerned in each step, 

 or to name all the intermediate products formed. For the 

 student of the soil the first consideration is a knowledge of 



^ Huteliinson, H. B., and Miller, N. H. J., The Direct Assimilation of 

 Inorgamc and Organic Forms of Nitrogen 'by Higher Plants; Centrlb, f . 

 Bakt., II, Band 30, Seite 513-547, 1911. 



