BLETTING. All ripe fruits after they have been kept for some time begin to decompose, and the spots formed on the fruit during this process have been called by Professor Lindley Blets.' During the whole time of the growth of the fruits of plants various important chemical changes go on in their tissues, especially whilst ripening. These changes have been examined with great care by Berard. At first the flesh of most fruits consists of fibrous or cellular tissue, which is mostly composed of lignine. The liquid of fruits is nap, which exists between the cella in the intercellular passages. This liquid, besides a great quantity of water, contains sugar, gum, malic acid, malato of lime, colouring matter, a peculiar vegeta-animal substance (protein), and an aromatic secretion proper to each fruit. In such fruits as the grape there is tartrate of potash and lime ; in the lemon and the gooseberry, citric acid. As the process of ripening goes on, the quantity of water diminishes, and the sugar increases. This sugar is formed at the expense of the lignine, and is either in a concrete state, as in the grape, fig, and peach, or fluid, as in most fruits. It is after this period that Bletting comes on, and changes take place in the fruit which render it unfit for the ordinary uses of man. Bletting he attended with the formation of carbonic acid, the nitrogenieed substance enters into a state of putrefaction, and the sugar undergoes fermentation. These processes are undergone most rapidly when the fruit is exposed to the action of the oxygen of the atmosphere. The fruits in which these changes have been most accurately observed are the pear and the apple. A jargonclle pear was found to have sustained a lose of its constituents in the following proportion :— Pipe. III( tied.
I.ignine . . • 29 9 . . . P85 Sugar . . 11'52 . . . 817 Water . . . 83'88 . . . 6213 It acquired rather more malic acid, gum, and nitrogenised matter.
The fact has been observed by Dr. Hamall that in all blotted fruits there exists a low form of Fungus, which he considers the cause of the decay. He found, on inoculating sound fruits, even while growing en the tree, that he could produce immediately the process of decay, and wherever this was indicated by blotting, there he discovered the fibres of the fungus with the microscope. This appearance of the fungus however is only in accordance with what we know of the habits of fungi, whose sporulee, being everywhere diffused through the air, immediately spring up where a fitting nidus is found for their growth. We find that as soon as a fruit becomes ripe its constituents commence union with the oxygen of the air, forming carbonic acid gas, and it is during this state of their elements that the fungus finds a soil ready for its development.
Whichever view be taken of the rotting of fruits, their preservation must be conducted en the same principle, for what will exclude oxygen will exclude the sporules of fungi. As a simple process it has been recommended to place at the bottom of a bottle a paste formed of lime, sulphate of iron, and water, and then to introduce the fruit, which has been pulled a few days before ripening. The fruits should be kept from the bottom of the bottle and as much as possible from each other, and the bottle should be closed by a cork and cement. In this way peaches, prunes, and apricots may be kept from 20 days to a month ; pears and apples for three months. Dr. Hassell recom mends that fruits should be washed over with a composition consisting of water one pound, shell-lac and borax two ounces.
(Lindley, Introduction to Botany; Hassell, Transactions of Micro scopical Society, voL i.)