oj Plants, in Charcoal. 253 



these sorts of matter can only be absorbed by the roots in pro- 

 portion as they are in a fluid or dissolved state in the soil. 

 These sorts of matter, and particularly the different organic 

 salts which we find in the ashes of vegetables, are not actually 

 to be considered sources of nourishment, but stimulants to as- 

 sist in digestion, as salt and spice are to the higher animals and 

 man. 



In connection with the subject Dr. Buckner introduces a 

 treatise by M. Payen, read before the Academy of Sciences 

 at Paris, on the 8th and 14th October, 1839, viz: — that char- 

 coal operates as a condenser, under the influence of water, on 

 the constituent parts of the air, in the same manner as spongy 

 platina on the elements of detonating gas; so that nitrogen and 

 oxygen are dissolved, and, mixing with water, are absorbed 

 by the spongioles, and carried to the cambium for assimilation. 

 This property of condensing the air, and making it fit to be 

 received by plants, does not exclusively belong to charcoal; 

 but charcoal powder appears to possess this power in the high- 

 est degree, consequently, besides light and heat, is capable of 

 carrying to the roots both air and water, i. e. nitrogen, hydro- 

 gen and oxygen, in the greatest abundance. 



3. Decomposition of the charcoal, and formation of a nour- 

 ishing substance for plants. — For a long time it was generally 

 believed that charcoal, as an inanimate body, incapable of de- 

 cay, contributed in no degree to the nourishment of plants, 

 and that charcoal dust could only serve at most to make the 

 earth looser and warmer. But M. Lucas found from his ex- 

 periments, that the charcoal, in which plants grow, by degrees 

 undergoes decomposition, and at last becomes a sort of hu- 

 mus. This obviously takes place merely because the char- 

 coal dust acts as humus, and with the co-operation of water 

 and air, continually gives out to the plants oxide of charcoal, 

 or carbonate, together with the saline particles which are in 

 the charcoal and remain in the ashes after burning. But to 

 prove this, some chemical experiments were necessary. 



4. Comparative chemical examination of charcoal dust. — 

 The more perfectly to establish the theory of the effect of 

 charcoal on vegetation, M. Lucas gave me for examination, 



1st. Ashes of fir [or pine] charcoal, in which no plant had grown. 

 2c'i. Ashes of fir charcoal, in which plants had been grown for 

 -li.alf a year. [This was used for most of the experiments.] 



3d. A portion of charcoal dust which had been used for another 

 purpose for two years, [to fill up a bed for plunging in plants.] 



