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6. 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 that produced under the influence of night and darkness, demonstrates that they decompose carbonic acid.”
In ripening, fruits undergo some remarkable alterations, which have been thus explained by De Candolle, in his abridgement of Bérard'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, especially in very fleshy fruits, lighter, less tough, and more easily soluble in alkaline solutions, than common lignine; but presenting 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 consists 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, besides a great quantity of water, contains 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.” Bérard 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,
“ Water before Water at
ripeness. ripeness. “ Apricots
89.39 74.87 Currants
86.41 81.10 Duke Cherries
88.28 74.85 Green Gages
74.87 71•10 Melting Peaches
90:31 80.24 Jargonelle Pears
86.28 83.88 “ This diminution appears to depend in part upon the fruit absorbing less water as it approaches maturity, and in part upon the combination with its tissue of a portion of the water it has received. Sugar, on the contrary, appears to be continually on the increase, as indeed the taste would tell us ; thus we find, per cent,
Ripe. “ Apricots (a trace when young, ,
1•12 18.12 Green Gage Plums
17071 24.81 Melting Peaches
is sometimes in a state more or less concrete, as in the Grape, the Fig, and the Peach; sometimes in a liquid state. It seems to be formed at the expense of other matters, the proportion of which diminishes. Thus the quantity of lignine per cent is found
Ripe. “ Apricots
3.61 1.86 Currants (including the seeds) 8:45 8:01 Duke Cherries
2:44 1:12 Green Gage Plums
1.26 1:11 Melting Peaches
3:01 1.21 Jargonelle Pears.
3.8 2:19 “ It is possible, indeed, that the lignine formed in the green fruit does not in reality diminish, but that the dilatation of the cellular tissue, and consequently the augmentation of the aqueous products, render it proportionably less, without its being absolutely so. But the gummy, mucilaginous, or gelatinous matters, appear very susceptible of changing into sugar;
thus, Couverchel found that, if we treat Apple jelly with a vegetable acid dissolved in water, we obtain a sugar analogous to that of Grapes; that the gum of Peas, placed with oxalic acid, in a temperature of 125° Réaum., changed to sugar; that gum extracted from starch, if mixed with the juice of green Grapes, rendered the latter saccharine; and finally that tartaric acid will produce the same effect by aid of heat: this is the reason why most fruits become sweet when cooked.
6 Other matters offer remarkable disparities between one fruit and another: thus malic acid keeps diminishing in Apricots and Pears, augmenting in Currants, Cherries, Plums, and Peaches. Gum keeps diminishing in Currants, Cherries, Plums, and Pears, and augmenting in Apricots and Peaches. Animal matter keeps diminishing in Apricots and Plums, and increasing in Currants, Peaches, Cherries, and Pears. Lime, which never exists except in small quantity, seems generally to diminish, probably because evaporation becomes less with maturity.
“ After the period which is generally called that of ripeness, most fleshy fruits undergo a new kind of alteration; their flesh either rots or blets.* These two states of decomposition cannot, according to Bérard, take place, except by the action of the oxygen of the air, although he admits that a very small quantity only is sufficient to cause it. He succeeded in preserving for several months, with little alteration, the fleshy fruits which were the subjects of the foregoing experiments, by placing them in hydrogen or nitrogen gases. All fruits at this extreme period of their duration, whether they decay or whether they blet, form carbonic acid with their own bon and the oxygen of the air, and moreover disengage from their proper substance a certain quantity of carbonic acid.
“ Bletting is in particular a special alteration. I have remarked, in another place, that this condition is not well characterised in any other fruits than those of Ebenaceæ and Pomaceæ; that both these natural orders agree in having the calyx adherent to the ovary, and that their fruits are austere before ripening
* May I be forgiven for coining a word to express that peculiar bruised appearance in some fruits, called blessi by the French, for which we have no equivalent English expression ?
It would even seem, from the fruits of Diospyros, the Sorb, and the Medlar, that the more austere a fruit is, the more it is capable of bletting regularly.
“ It has been found that a Jargonelle Pear, in passing to this state, loses a great deal of water (83.88 reduced to 62:73), pretty much sugar (11.52 reduced to 8:77), and a little lignine (2:19 reduced to 1.85); but acquires rather more malic acid, gum, and animal matter. Lignine, in particular, seems, in this kind of alteration, to undergo a change analogous to that of wood in decay.”
The foregoing experiments have led to the discovery, that fruits which do not require to remain on the tree may be preserved for some time, and thus the pleasure they afford us prolonged. A simple process is said to consist in placing, at the bottom of a bottle, a paste formed of lime, sulphate of iron, and water, and afterwards introducing the fruit, it having been pulled a few days before it would have been ripe. Such fruits are to be kept from the bottom of the bottle, and, as much as possible from each other; and the bottle is to be closed by a cork and cement. The fruits are thus placed in an atmosphere free from oxygen, and may be preserved for a longer or shorter time, according to their nature: Peaches, Prunes, and Apricots, from twenty days to a month;. Pears and Apples for three months. If they are withdrawn after this time, and exposed to the air, they ripen well; but, if the times mentioned are much exceeded, they undergo a particular alteration, and will not ripen at all.
OF THE SEED.
The action of the seed is confined to that phenomenon which occurs when the embryo that the seed contains is first called into life, and which is named germination.
If seeds are sown as soon as they are gathered, they generally vegetate, at the latest, in the ensuing spring; but, if they are dried first, it often happens that they will lie a whole year or more in the ground without altering. This character varies extremely in different species. The power of preserving their vitality is also variable: some will retain their germinating powers many years, in any latitude, and under almost any circumstances. Melon seeds have been known to grow when 41 years old, Maize 30 years, Rye 40 years, the Sensitive plant 60 years, Kidneybeans 100 years. Clover will come up from soil newly brought to the surface of the earth, in places in which no clover had been previously known to grow in the memory of man, and I have at this moment 3 plants of Raspberries before me, which have been raised in the garden of the Horticultural Society from seeds taken from the stomach of a man, whose skeleton was found 30 feet below the surface of the earth, at the bottom of a barrow which was opened near Dorchester. He had been buried with some coins of the Emperor Hadrian, and it is therefore probable that the seeds were sixteen or seventeen hundred years old.
The chemical action of seeds has been well explained by De Candolle, to whom, however, the recent observations by Edwards and Colin were unknown.
Water, heat, and atmospheric air (or at least oxygen) are the conditions without which germination cannot take place. If any one of them is abstracted, the other two are of no