8 Theory of Jigucidture. [Jan., 



be introduced into a crop of wheat straw, would be only 93 lbs. 

 which w^ould correspond to 63 lbs. of humic acid. So also it is 

 shown that the quantity of humates which can be introduced 

 through the medium of rain water, providing none of it was lost by 

 evaporation, is totally iusufficient to meet the demands of any 

 growing cultivated crop. A Hessian acre receives 1 7 1,000 lbs. of 

 rain water daring the months of April, May, June, and July, the 

 four months during which the matter of grown crops is accumu- 

 lated. This quantity of w^ater will take up and convey to the 

 tissue of plants only 330 parts of humic acid, since one part ol 

 humic acid requires 2,500 parts of water for solution. 



But the same quantity of land produces 2,843 lbs. of corn, ex- 

 clusive of roots; 22,000 lbs. of beet, exclusive of leaves and 

 radical fibres; 2,920 lbs. of wood, consisting of firs, beeches, 

 pines, &c. ; and 2,755 lbs. of hay. One hundred parts of dry 

 fir-wood contain 38 parts of carbon, which amounts to 1,109 

 of carbon in 2,920 lbs. One hundred parts o-f hay contain 44.31 

 parts of carbon, equalling 1,111 of carbon in 2,755 lbs. In 

 22,000 lbs. of beet root there are ] ,032 lbs. of carbon, of w^hich 

 833 lbs. belong to the sugar, and 198 lbs. to the cellular tissue. 

 One hundred pounds of straw contain 745 of carbon, hence 1,961 

 dry straw yield 745 lbs. carbon. 



From these facts Liebig founds the doctrine that humus or 

 mould is not the source from which plants derive their carbon, 

 and as the atmosphere is the only great reservoir of carbon, from 

 it plants must of necessity obtain this element. 



To this doctrine Bousingault also subscribes. He says that* 

 the decomposition of carbonic acid by plants is admitted; we 

 have still to examine whether, in the phenomena of vegetation, 

 the leaves decompose the carbonic acid of the atmosphere direct- 

 ly, or the acid gas previously dissolved in the water which mois- 

 tens the ground, and thus be conducted by the way of absorption 

 into the tissues of vegetables, theie to suffer decomposition. This 

 question, wdiether the carbonic acid in the tissues, is derived from 



* Rural Economy, p. 40, 



