CHAP. VII. 
FRUIT. 
293 
from ripeness than when they are approaching that state. If 
exposed to the sun, they disengage altogether or in part the 
oxygen which they inspired during the night, and preserve no 
trace of this acid in their own atmosphere. If many fruits are 
detached from the plant, they thus add oxygen to air which 
contains no carbonic acid. When their vegetation is very 
feeble, or extremely languid, they vitiate the air under all cir- 
cumstances, but less in the sun than in the shade. Green 
fruits detached from a plant, and exposed successively to the 
action of the sun and of darkness, change it but little or not 
at all either in purity or in volume. The trifling variations 
that may be remarked in this respect depend either upon the 
greater or less faculty which they have of elaborating carbonic 
acid, or in their composition, which is modified according to 
the degree of their ripeness. Thus Grapes, in a state of ver- 
juice, appear to assimilate in small quantity the oxygen of the 
carbonic acid which they form in the air where they vegetate 
both day and night ; while, on the contrary. Grapes nearly 
ripe give back almost entirely during the day to their own 
atmosphere the oxygen of the carbonic acid they have formed 
in darkness. If there is no deception in this circumstance, 
which, although feeble, appears to have been constant, it 
marks the passage from the acid to the sweet state by indi- 
cating that the acidity of verjuice depends upon the fixing of 
the oxygen of the air, and that this acidity disappears when 
the fruit no longer seeks for carbon in the air or in carbonic 
acid. Green fruits decompose, either entirely or in part, not 
only the carbonic acid they have produced during the night, 
but, in addition, such quantity as may be artificially added to 
their atmosphere. When this last experiment is tried with 
fruits which are not watery, and which, like Apples and 
Grapes, elaborate but slowly carbonic acid, one sees that they 
absorb in the sun a much larger proportion of gas than the 
same volume of water in a similar mixture ; afterwards they 
disengage the oxygen of the carbonic acid absorbed, and thus 
appear to elaborate it in their interior. 
" They appropriate to themselves during their vegetation 
both oxygen and water, compelling the latter to lose its liquid 
state. 
V 3 
