I9I3.] SCHREINER— TOXIC SOIL SUBSTANCES. 421 



ever giving rise to new compounds through decomposition or through 

 synthesis, compounds which have distinct properties to influence 

 plant growth or other biological activity in soils. With this knowl- 

 edge comes the broader view that infertility in soils may as well be 

 due to the presence of organic substances of biological origin inimical 

 to proper plant development as to the absence of beneficial mineral 

 elements. The existence of toxic organic compounds in soils has 

 been amply shown by the researches of the Bureau of Soils into the 

 nature of soil organic matter in infertile soils, and the properties of 

 the isolated compounds in respect to their action on plants, so that 

 the presence of toxic compounds in soils must be considered in con- 

 nection with future work on the problems presented by infertile soils. 

 The scope of the investigation has necessarily been broader than 

 a mere search for toxic substances and has included soil organic 

 matter in general with the result that many organic compounds, both 

 harmful and beneficial, have been found in the course of the investi- 

 gation. With not a single soil compound isolated and identified a 

 few years ago, those now definitely identified are as follows : Acrylic 

 acid, adenine, agroceric acid, agrosterol, arginine, choline, creati- 

 nine, cytosine, dihydroxystearic acid, glycerides, guanine, hentria- 

 contane, histidine, hypoxanthine, lignoceric acid, lysine, mannite, 

 monohydroxystearic acid, nucleic acid, oxalic acid, paraffinic acid, 

 pentosan, pentose, phytosterol, picoline carboxylic acid, resin, resin 

 acids, resin esters, rhamnose, saccharic acid, salicylic aldehyde, suc- 

 cinic acid, trimethylamine, trithiobenzaldehyde, xanthine. A glance 

 at the list will reveal the fact that most chemical classes are repre- 

 sented : hydrocarbons, acids and hydroxyacids, alcohols, aldehydes, 

 esters, carbohydrates, hexone bases, purine bases, pyrimidine deriva- 

 tives, sulphur compounds, etc. Most of them have been derived 

 by biochemical changes taking place within the soil from the more 

 complex compounds, from the fats, nucleoproteins, proteins, lecithins, 

 etc. For instance, we may trace the complex nucleoprotein molecule 

 through its various decompositions, first into protein and a complex 

 nucleic acid which can further yield protein and nucleic acid. The 

 protein resolves itself finally into such compounds as histidine, argi- 

 nine, lysine, and possibly creatinine, all of which we have found in 



