56 The Chemical Statics of Organised Beings. 



also observed enormous quantities of carbonic acid escape from 

 the divided trunk of trees in full sap, evidently drawn by the 

 roots from the soil. 



But if the roots imbibe this carbonic acid within the earth, if 

 this passes into the stalk and thence into the leaves, it ends by 

 being exhaled into the atmosphere, without alteration, when no 

 new force intervenes. 



Such is the case with plants vegetating in the shade or at 

 night. The carbonic acid of the earth filters through their 

 tissues, and diffuses itself in the air. We say that plants pro- 

 duce carbonic acid during the night; we should say, in such 

 a case, that plants transmit the carbonic acid borrowed from the 

 soil. 



But let this carbonic acid, proceeding from the soil or taken 

 from the atmosphere, come into contact with the leaves or the 

 green parts, and let the solar light moreover intervene, then the 

 scene all at once changes. 



The carbonic acid disappears ; bubbles of free oxygen arise 

 on all the parts of the leaf, and the carbon fixes itself in the 

 tissues of the plant. 



It is a circumstance well worthy of interest, that these green 

 parts of plants, the only ones which up to this time manifest 

 this admirable phenomenon of the decomposition of carbonic 

 acid, are also endowed with another property not less peculiar, 

 or less mysterious. 



In fact, if their image were to be transferred into the ap- 

 paratus of M. Daguerre, these green parts are not found to be 

 reproduced there; as if all the chemical rays, essential to the 

 Daguerrian phenomena, had disappeared in the leaf, absorbed 

 and retained by it. 



The chemical rays of light disappear, therefore, entirely in 

 the green parts of plants; an extraordinary absorption doubt- 

 less, but which explains without difficulty the enormous expense 

 of chemical force necessary for the decomposition of a body so 

 stable as carbonic acid. 



What, moreover, is the function of this fixed carbon in the 

 plant ? for what is it destined ? For the greater part, without 

 doubt, it combines with water or with its elements, thus giving 

 birth to matters of the highest importance for the vegetable. 



If twelve molecules of carbonic acid are decomposed and 

 abandon their oxygen, the result will be twelve molecules of 

 carbon ; which, with ten molecules of water, may constitute 

 either the cellular tissue of plants, or their ligneous tissue, or 

 the starch and the dextrine which are produced from them. 



Thus, in any plant whatever, nearly the entire mass of the 

 structure (charpente), formed as it is of cellular tissue, of lig- 

 neous tissue, of starch, or of gummy matters, will be repre- 



