294 
PHYSIOLOGY. 
BOOK II. 
" These results are often not observable in volumes of air 
less than from 30 to 40 times that of the volume of the fruit, 
and by diminishing the heating power of the sun. If such 
precautions are neglected, many fruits will vitiate the air even 
in the sun by forming carbonic acid with the ambient oxygen ; 
but, even in the latter case, the simple comparison of their 
effect in light, with what they produce under the influence of 
night and darkness, demonstrates that they decompose car- 
bonic acid." 
In ripening, fruits undergo some remarkable alterations, 
which have been extremely well explained by De Candolle 
in his condensations of Berard's observations : — 
" If we examine the modifications which the flesh of fruits 
undergoes in ripening, we shall at first remark that their 
fibrous or cellular tissue (which varies very much in quantity 
in different species) is merely lignine : in most cases, espe- 
cially in very fleshy fruits, lighter, less tough, and more easily 
soluble in alkaline solutions than common lignine ; but pre- 
senting characters of an opposite kind in other parts of the 
same fruit, such as their stones. 
" The liquid which fills the flesh of succulent pericarps con- 
sists of sap placed in the intercellular passages and of the 
matter contained in the cells. This liquid of the flesh, or of 
the fleshy endocarp, contains, besides a great quantity of 
water, sugar, gum, malic acid, malate of lime, colouring 
matter, a peculiar vegeto-animal substance, and an aromatic 
secretion proper to each fruit : there is, moreover, in certain 
cases, the tartrates both of potash and of lime, as in Grapes ; 
and citric acid in the Lemon, and even in small quantity 
in the Gooseberry." Berard could find no trace of starch in 
watery fruits, such as Cherries, Plums, Peaches, Currants, 
Grapes, nor even in Pears and Apples, although it has been 
said to exist in them. 
" A comparison of the analysis of certain fruits, before they 
are ripe and at that period, gives some curious results. In 
the first place there is a disappearance of water in a liquid 
state, viz., per cent, — 
