(Srass Spaces 125 



position of humus, but we can study the kinds of 

 decompositions and recombinations that are going 

 on in it and that result in making it a suitable food 

 for plants. In this study we must ever keep in mind 

 the fact that dead bodies of animals and plants are 

 not in condition to serve another generation of 

 plants as food. We cannot feed plants upon eggs, 

 or urine, or starches, or sugars. Though containing 

 carbon and nitrogen in abundance, these elements 

 are locked up in them out of the reach of the green 

 plants, and before they can be utilized again they 

 must be freed from their combinations and brought 

 into simpler forms. This is accomplished by the 

 micro-organisms (bacteria) in the soil. Our study 

 of these changes may best be centred around the two 

 chemical elements, carbon and nitrogen. 



"Farming without the aid of bacteria would be 

 an impossibiUty, for the soil would yield no crops." ^ 



Concerning the value of humus as a fertilizer many 

 authorities may be quoted besides those in the footnote. '' 



' See Agricultural Bacteriology, H. W. Conn, Prof. Biology in 

 Wesleyan University, Connecticut, U. S., 2d edition, p. 39. 



'Peat, Its Uses as Fertilizer and Fuel, S. W. Johnson, p. 90, ed. 1859. 

 Also Soil, etc., by Dr. E. W. Hilgard, Professor of Agriculture in the 

 University of CaUfomia and Director of the California Agricultural 

 Experiment Station, ed. 1907, chapter v., pp., 72, 73, 74; chapter viii., 

 chapter ix. Also in Peat and Muck, etc., by Saml. W. Johnson, Pro- 

 fessor of Agricultural Chemistry, Yale College, U. S., edition 1859, pp. 

 67, 80, 81, 82; p. 107, Ans. 14; p. 109, Ans. 14; p. 113, Ans. 14; p- 

 121, Ans. 14; p. 145, Ans. 13; Remarks, 147, Ans. 13; Remarks, 149. 

 Ans. 13. Also Soils, etc., S. W. Fletcher, Professor of Horticulture, 

 Michigan Agricultural College, chapter iii., pp. 60, 61, 62; chapter xiii. 



