244 
by heat, was placed in a phial containing pure 
water in which a plant of peppermint was grow- 
ing : the roots of the plant were pretty generally 
in contact with the charcoal. The experiment was 
made in the beginning of May, 1805 ; the growth 
of the plant was very vigorous during a fortnight, 
when it was taken out of the phial : the roots were 
cut through in different parts ; blit no carbonaceous 
matter could be discovered in them, nor were the 
smallest fibrils blackened by charcoal, though this 
must have been the case had the charcoal been 
absorbed in a solid form. 
No substance is more necessary to plants than 
carbonaceous matter ; and if this cannot be intro- 
duced into the organs of plants except in a state 
of solution, there is every reason to suppose that 
other substances less essential will be in the same 
case. 
I found by some experiments made in 1804, that 
plants introduced into strong fresh solutions of 
sugar, mucilage, tanning principle, jelly, and other 
substances, died ; but that plants lived in the same 
solutions after they had fermented. At that time, 
I supposed that fermentation was necessary to pre- 
pare the food of plants ; but I have since found 
that the deleterious effect of the recent vegetable 
solutions was owing to their being too concentrated ; 
in consequence of which the vegetable organs were 
probably clogged with solid matter, and the trans- 
piration by the leaves prevented. In the beginning 
of June, in the next year, I used solutions of the 
same substances, but so much diluted, that there 
was only about *&?> part of solid vegetable or animal 
