• FOOUOF PLANTS. 17 



non, the decomposition of carbonic acid, are also possessed of ano- 

 ther property, not less peculiar, not less mysterious. 



" If we attempt to transfer their images to a prepared plate of 

 the apparatus of M. Daguerre, the green parts are found not to be 

 reproduced, not to be formed ; it is as if the whole of the chemical 

 rays essential to the photographic phenomenon had disappeared, 

 iiad been absorbed and retained by the leaf. 



" It would seem, therefore, that the chemical rays of light van- 

 ish entirely in the green parts of plants — an extraordinary absorp- 

 tion without doubt, but easily explained when the enormous ex- 

 penditure of chemical force necessary to the decomposition of a 

 substance so stable as carbonic acid is required. 



" Let us next inquire concerning the part played by the carbon 

 thus wonderfully fixed by vegetables. What is its business — 

 what its destination 1 For the major part unquestionably, it com- 

 bines with water or its elements, and it thus gives origin to sub- 

 stances of the highest consequence in the economy of plants. 



" Twelve atoms of carbonic acid being decomposed and aban- 

 doning their oxygen, there will result twelve atoms of carbon, 

 which, with ten atoms of water, will compose either the cellular 

 or the ligneous tissue of plants, or the starch and dextrine which 

 are their derivatives."* 



Such is the important part which is played by carbonic acid as 

 an article of the food of plants. Introduced into their interior, 

 whether by the roots or by the leaves, it is, under the influence of 

 the sun's rays, decomposed in the green parts, its carbon remains 

 in the plant and the oxygen is exhaled into the atmosphere. The 

 carbon then unites with the water or its elements, and forms starch, 

 sugar, gum and the other non-nitrogenized principles. 



The action of plants is in this respect precisely the reverse of 

 what takes place in animals. The latter consume the carbon in 

 their food, which ultimately combines with the oxygen introduced 

 by the lungs, and is converted into carbonic acid, which passes 

 into the atmosphere, and is by plants again resolved into carbon 

 and oxygen. For this reason plants have been called apparatus 

 of reduction, and animals apparatus of combustion. 



The carbonic acid is derived from the soil, where it is genera- 



* Dumas' Balance of Organic Nature. 

 VOL. I. — NO. 1. C 



