194 ORIGIN OF ORGANIC MATTER 



more delicate structure of plants, and the constant occurrence of 

 certain substances such as organic acids, the so-called carbo- 

 hydrates, and albuminous matters in all plants, without exception, 

 seem to afford an explanation of certain phenomena ; the endless 

 variety of those secondary products, which are peculiar to almost 

 every plant, throws such obstacles in the way of our inquiries that 

 we can scarcely hope to give even a hypothetical representation of 

 the formation of organic matter within the plant. 



The entire vegetable organism is scarcely anything more than 

 a system of cells, within which various substances are undergoing 

 metamorphoses, and organic matter is passing through the earliest 

 stages of its formation. The ammonia which penetrates into the 

 roots, combined with sulphuric or carbonic acid, according to 

 Liebig, or with humic acid, according to Mulder, must have passed 

 through the cells of the fibrils of the roots. The decomposition 

 of carbonic acid can only take place within the green cells of the 

 plant, for the most torn leaf may continue to exercise the function 

 of absorbing carbonic acid and giving off oxygen ; but when once 

 its cells are crushed or otherwise destroyed, this vital process 

 ceases. Hence we are led to conclude, that in the cell-membrane, 

 or, in other words, in the morphological relations of the cell, there 

 is as important an agent for this process of metamorphosis as in 

 the chemical character of the cell-contents. We have already 

 frequently remarked that our present knowledge of endosmosis 

 and diffusion is not sufficient to lead us to the correct interpre- 

 tation of vital processes. Discoveries such as Graham's, that the 

 chemical union of certain substances may be broken by simple 

 diffusion, lead us to anticipate that many obscure points connected 

 with these vital processes may be elucidated, and that we may at 

 length be enabled to determine with some degree of accuracy, the 

 results which would be produced by bringing heterogeneous matters 

 in contact with a cell of certain dimensions, definite thickness of 

 the cell-membrane, known contents, &c. At present we are only 

 able to conjecture in the most general manner the mode in which 

 certain physical and chemical processes are effected by the agency 

 of cells. We are especially indebted to Mulder* for pointing out 

 the various modes in which cell-formations may possibly contri- 

 bute towards the vital economy of the plant. 



We next pass to the consideration of the formation of those 

 non-nitrogenous substances, which are common to all plants, 

 and are especially characterised by containing, in addition to 

 * Vers. einer physiol. Chem. S. 781-791 [or English translation, pp. 716-725]. 



