208 EXPEEIMENT STATION RECORD. 



twenty compounds found in the organic matter of the soil. These 

 comiDOunds belong to eight or more different classes, as paraffin hydro- 

 carbons, acids, alcohols, esters, carbohydrates, hexone bases, pyrimi- 

 dine derivatives, and purine bases. 



While this work shows clearh^ the complex character of the organic 

 matter of the soil, it also encourages the hope that the exact chemical 

 nature of all of the organic constituents of the soil may ultimateW be 

 determined by modern methods of research, thus furnishing a safe 

 basis for further study of the origin and properties of the com- 

 pounds and their relation to soil fertility and productiveness, which 

 has not heretofore been available. Such exact knowledge will prove 

 of great assistance in the investigation of all soil problems in which 

 the organic matter is the paramount factor. 



Of like importance is the work of Jodidi and others, in which 

 known methods of investigation of proteids are being applied in the 

 stud}^ of the decomposition products of nitrogenous bodies in the 

 soil. This work promises to show definitely the chemical character of 

 the nitrogenous bodies present in the soil and the processes by which 

 they are formed, thus furnishing an exact basis for studying the rela- 

 tion of these bodies to the nitrogen nutrition of plants, a point on 

 which surprisingly little is actually known notwithstanding the fact 

 that great significance has been usually and perhaps righth^ attached 

 to humus as a source of nitrogen for plants. The relation of humus 

 to the availabilit}' of the mineral plant food of the soil, a subject 

 not now Avell understood despite the fact that it has received much 

 investigation, can only be full}^ cleared up when studied in the light 

 of exact knowledge of the compounds involved. 



Bacteriological investigation of the soil has brought out very 

 clearly the fact that, aside from its recognized physical effects and 

 function as a source of supply of nitrogen and perhaps other plant 

 food, the organic matter of the soil is a most important factor in 

 soil fertility as a source of food to the micro-organisms, which in- 

 crease and elaborate food for higher plants. A knowledge of the 

 exact composition of the organic compounds formed in the soil under 

 different conditions will perhaps make it possible to control in a 

 measure the character of the organic compounds produced and thus 

 the bacterial activity of the soil. 



Evidently no work on humus which does not take account of the 

 very complex and varying character of the group embraced by this 

 term can be expected to give intelligent or final results. Humus is 

 a generic term, as "• mineral matter " is. Considered as a substance, 

 we are dealing with something whose character in a given case is 

 quite unknown, and whose response to tests and reactions or whose 

 effect on plant life can not be foreseen. It is only as these facts are 

 recognized that real progress in this line of studj^ can be looked for. 



