Researches on the Action of Fohage. 241 
In a continuation of these investigations (Comptes 
Rendus, vol. \xi., Sept. 25, 1865), Boussingault shows that 
carbonic oxide, whether pure or diluted, is not decom- 
posable by foliage, and that this inertness of green foliage 
upon carbonic oxide goes: to confirm the opinion main- 
tained in his Economie Rurale, that leaves simultaneously 
decompose carbonic acid and water, CO,, HO=CO, H,0O ; 
the O, being liberated, CO,H expresses the relation under 
which carbon is united with the elements of water in 
cellulose, starch, sugar, etc.—ze, in the important prin- 
ciples elaborated by the leaves, the composition of which 
is represented by carbon and water. He goes on to prove 
that a leaf which has been decomposing carbonic acid and 
water all day long is capable of doing the same work 
the next day, if not allowed to dry, but the losing of a 
certain amount of water annihilates this faculty, and 
irremediably destroys the life of the cells of a leaf, 
vegetable life in this state being far less tenacious than 
that of some of the lower animals (7ardigrades, Notipes, 
&c.), which bear wonderful desiccation. 
The third instalment of the investigation is given in 
Nos. 16 and 17 of the same volume (Oct. 16 and 23, 1865). 
It appears that detached leaves, kept in shade for many 
days, with the cut end of the petiole in water to prevent 
dessication, preserve the power of decomposing carbonic 
acid whenever brought into sunshine. But for this they 
must be kept in an atmosphere containing a supply of 
oxygen; without this they soon die, as Boussingault thinks 
from asphyxia. The oxygen in darkness is slowly trans- 
formed into carbonic acid, through an operation which is 
presumed to go on continually, whether in light or dark- 
ness, and to answer to respiration. Of course a healthy 
and active leaf decomposes far more carbonic acid in the 
light than it forms in darkness. In eighteen experiments, 
with Oleander-leaves exposed to the sun from eight A.M. 
to five P.M., in an atmosphere rich in carbonic acid, a 
Square metre of foliage decomposed on the average over a 
litre of carbonic acid per hour, while in darkness only x30 of 
a litre of carbonic acid was produced per hour. In air which 
contains oxygen and carbonic acid, leaves will go on indefi- 
nitely producing oxygen in the presence of carbonic acid 
and carbonic acid in the presence of oxygen. But the 
latter, though relatively small in amount, seems to be 
necessary to the preservation of their vitality. In hydro- 
gen, carburetted hydrogen or nitrogen, as well as in pure 
NEW SERIES.—VOL. I. Xx 
