into the Practices and Results of Horticulture. 399 



substances, and particularly for the oxj-gen and hydrogen gases, 

 it cannot be obtained in a pure and separate state, and that it 

 cannot be exhibited, or its existence proved, by any other man- 

 ner than by its effects. Before any judgment could be formed as 

 to the best mode of obtaining and applying carbon as food for 

 plants, it must have been necessary to ascertain what capacities 

 are possessed by plants for feeding, or supplying themselves 

 with nutriment; and to do this, plants have been submitted to 

 anatomical examination, aided by the solar microscope, and it 

 appears that they are furnished with no other organs of sup- 

 ply than the roots, and those, being covered by a fine sponge- 

 like substance, cannot take into their bodies, or consume, any 

 thing that is not in a perfect state of solution, and blended 

 with water ; and this conclusion has been confirmed by many 

 direct experiments. Hence it must be obvious, that, to fur- 

 nish the earth with the nutritive principle, it is not sufficient 

 to supply carbon, or any substance containing carbon in a crude 

 and insoluble state; it must be reduced to a state of solution 

 in water, or to a state capable of- being dissolved by water, 

 before it can be appropriated by plants ; and here, again, the 

 chemists are at a stand. The only solution of carbon which 

 they exhibit is that of carbonic acid gas, or carburetted hydro- 

 gen gas, and this has been, by some, considered to be the food 

 of plants ; but it is found by experiment, that carbon in this 

 state cannot be made available to plants. 



Although, then, the chemists have made us acquainted with 

 the elements of all those compound substances, which are re- 

 quired to be brought together in the cultivation of vegetables, 

 and thus have enabled ns to determine that carbon is the grand 

 fertilising principle, our powers are not much increased by 

 such discoveries ; as, after all, we are left to do that which 

 gardeners have ever done, — that is, to supply the earth with 

 animal and vegetable matter, and leave it to nature to prepare 

 and reduce the carbon to a proper state for the sustenance of 

 plants. And, notwithstanding it is proved that carbon is the 

 fertilising principle, and that it can only be furnished by the 

 decomposition of animal and vegetable substances, it is well' 

 known that the result of such decompositions, when produced 

 under certain circumstances, will not impart fertility ; which is 

 found to be the case with the residuum of animal and vegeta- 

 ble matters, decomposed deep under the earth, or in stagnant 

 water. It is evident, then, that some other principle must be 

 combined with carbon, to render it available to plants ; and, 

 therefore, the discovery of this principle must be an object of 

 equal value to that which has been discovered in carbon. And 

 here, again, it may be observed, the chemists have not sue- 



