Academy of Sciences in Paris. 353 



acid at the ordinary temperature of the atmosphere, is adapted for the 

 nutrition of plants. This carbon is to be found in the extractive 

 matter which abounds in vegetable earth, and which is also found in 

 solution in all waters, even in the most apparently pure springs. 

 This carbon exists also in an organic matter which is as volatile as 

 the water in which it is dissolved. When water, charged with organic 

 substances, is distilled, water is obtained which is not pure, it 

 contains a matter which, if not organic, is at least organizable. 

 This water, when exposed to the light, develops and produces the 

 green matter of Priestley, and the Vaucheria infusoria, which proves 

 that it contains alimentary matter. When the water contains a con- 

 siderable quantity of this matter it is sensible to the taste ; but otherwise 

 its presence cannot be detected, as it is not affected by any chemical 

 re-agent. The volatility of this organizable matter proves that it must 

 exist in the water which is evaporated from the surface of the globe. 

 When this water falls again in the shape of rain, it meets, in its 

 course through the atmosphere, volatile emanations both animal and 

 vegetable, with which it becomes charged, and thus rain-water, dis- 

 tilled by Nature herself, falls charged with matters adapted for the 

 nutrition of plants. Thus we perceive that, although part of the 

 nourishment of plants is obtained from the atmosphere, it is as much 

 derived from the carbon contained in the rain and dews, as from the 

 absorption of the atmospheric carbonic acid. But it must be ad- 

 mitted that the principal aliment is derived from the soil through the 

 roots. Boyle's experiment on a willow branch which, in five years, 

 increased in weight one hundred and sixty-five pounds, while the 

 earth in the pot in which it was planted had only diminished two 

 ounces, does not prove that the plant was alimented solely or princi- 

 pally by the atmospheric carbon, because it had been from time to 

 time watered with water more or less charged with extractive sub- 

 stance. It must be remarked that when plants constantly impart the 

 detritus of their leaves to the soil in which they grow, they enrich it 

 with alimentary carbon instead of exhausting it, which proves that a 

 portion of their alimentany carbon is derived from the atmosphere, but 

 that portion would be insufficient for their aliment if unassisted by the 

 carbon introduced through the medium of the roots. It results from 

 this two-fold origin of the alimentary carbon, that the plant in its annual 

 fall of leaves, and in its decomposition after death, communicates to 

 the soil more carbon than it had received from it. Every year, 

 therefore, that a tree lives, it not only enriches the soil in which it 

 grows, but it acquires more powerful sources of aliment, because to 

 the atmospheric carbon, the source of which is always the same, it 

 adds the earthy carbon, the quantity of which is annually augmented. 

 This earthy carbon necessarily becomes exhausted in the fields, 

 when we remove the vegetables which they have produced; thence 

 the necessity of replacing this carbon, or rather this extractive, by 

 the addition of manure. This may also be effected, although with 

 less advantage, by growing herbaceous plants and burying them in 



