252 M. De Saussure on the Infiaence of Green TruiU 
small degree, the quantity of oxygen, and formed carbonic acid. 
In an artificial mixture of gases, containing ^^^th part of carbo- 
nic acid, in which the experiment was continued through the 
day and night for four days, with the same plants, the carbonic 
acid in great part disappeared, and the oxygen was in a small 
degree diminished. 
Experiments were next made on the crab apple (Pyrus ma- 
ins)^ which, though it be green externally, has within a white 
colour. When exposed to the sun in vessels of spring water, it 
almost entirely decomposed the carbonic acid, and produced a 
corresponding quantity of oxygen gas. In experiments with 
this and similar fruits a weak sun is required ; for a very vivid 
one excites fermentation, and gives rise to different results. The 
leaves of the same tree disengaged oxygen very rapidly if the 
sun was vivid, and decomposed entirely the carbonic acid gas. 
When confined, in a I’ecipient of air through the night, the fruit, 
as in other instances, reduced the quantity of oxygen, and form- 
ed carbonic acid ; and when exposed alternately to night and 
day for forty-eight hours, the air lost only a very small portion 
of oxygen. In artificial mixtures, which contained about ^^^th 
part of carbonic acid, the proportion of oxygen was augmented, 
and the quantity of carbonic acid greatly reduced. Except on- 
ly in extent of power, apples, therefore, exert the same action 
on the air as their leaves. ~ 
Green grapes were next exposed to the sun in spring watei’, 
and produced an air, which, in 100 parts, contained 29 parts 
oxygen and 71 azote. The leaves of the grape, in the same 
circumstances, produced almost precisely the same effect ; and 
similar results were obtained with the green stems of the vine. 
A bunch of green grapes, confined in air through the night, di- 
minished its oxygen and produced carbonic acid. In the sun 
also, after forty-eight hours exposure to a strong light, the oxy- 
gen of the air was diminished by sour grapes^ and a portion of 
carbonic acid formed ; and when alternately exposed by night 
and day, for four days, to the successive action of light and dark- 
ness, the oxygen of the air was partially destroyed, and a little 
carbonic acid produced. If the grapes remained attached to the 
branch, while confined in the vesseil and exposed to the succes- 
sive action of light and darkness for twelve days, the air of the 
