"The pericarp is at first of a green color, and performs the same functions as the other green parts of plants, decomposing carbonic acid under the agency of light and liberating oxygen. Saussure asserts that all fruits, in a green state, are adequate to perform this process of deoxidation. As the pericarp advances to maturity, it either becomes dry or succulent. In the former case it changes into a brown or white color, and has a quantity of ligneous matter deposited in its substance, so as to acquire great hardness, where it is incapable of performing any process of vegetable life; in the latter it becomes fleshy in its texture, and assumes various bright tints. In fleshy fruits, however, there is frequently a deposition of ligneous cells in the endocarp, forming the stone of the fruit; and even in the pulpy matter of the sarcocarp, there are found isolated cells of a similar nature, as in some varieties of pear, where they cause a peculiar grittiness. The contents of the cells near the outside of succulent fruits are thickened by exhalation, and a process of endosmose goes on, by which the thinner contents of the inner cells pass outward, and thus cause swelling of the fruit. As the fruit advances to maturity, however, this exhalation diminishes, the water becoming free and entering into new combinations. In all pulpy fruits, which are not green, there are changes going on by which carbon is separated in combination with oxygen.

* * * "Succulent fruits contain a large quantity of water along with cellulose or lignine, sugar, gummy matter or dextrine, albumen, coloring matter, various organic acids, as citric, malic and tartaric, combined with lime and alkaline substances, beside a pulpy gelatinous matter, which is converted by acids into pectine, whence pectic acid is formed by the action of albumen. Pectine is soluble in water, and exists in the pulp of fruits, as apples, gooseberries, currants, strawberries, etc. Pectic acid is said to consist of C.14, H.3, O.12 + H.O. It absorbs water, and is changed into a jelly-like matter, hence its use in making preserves. Each kind of fruit is flavored with a peculiar aromatic substance. Starch is rarely present in the pericarp of the fruit, although it occurs commonly in the seed. * * *

"During the ripening much of the water disappears, while the cellulose or lignine and the dextrine are converted into sugar. Berard is of opinion that the changes in fruits are caused by the action of the oxygen of the air. Freney found that fruits, covered with varnish, did not ripen. As the process of ripening becomes perfected, the acids combine with alkalies, and thus the acidity of the fruit diminishes, while its sweetness increases. The formation of sugar is by some attributed to the action of organic acids on the vegetable constituents, gum, dextrine, and starch; others think that the cellulose and lignine are similarly changed, by the action of acids. The formation of sugar is said to be prevented by watering the tree with alkaline solutions. * * * In seasons, when there is little sun, but a great abundance of moisture, succulent fruits become watery and lose their flavor. The same thing frequently takes place in young trees with abundance of sap, and in cases where a large supply of water has been given artificially." Travelers, who have eaten the magnificent specimens of fruits produced by irrigation, in California, tell us that they are deficient in flavor, and the same thing is sometimes observed as a result of an unusually wet season.

"It is not easy in all cases to determine the exact time when the fruit is ripe. In dry fruits, the period immediately before dehiscence,[21] is considered as that of maturation; but in pulpy fruits, there is much uncertainty. It is usual to say that edible fruits are ripe when their ingredients are in such a state of combination as to give the most agreeable flavor. After such are ripe, in the ordinary sense, so as to be capable of being used for food, they undergo further changes by the oxidation of their tissues, even after being separated from the plant. In some cases these changes improve the quality of the fruit, as in the case of the medlar, the austerity of which is thus still further diminished. In the pear, this process renders it soft, but still fit for food, while in the apple it causes a decay which acts injuriously on its qualities. By this process of oxidation, the whole fruit is ultimately reduced to a putrescent mass, which probably acts beneficially in promoting the germination of the seeds when the fruit drops on the ground.

"The periods of time required for ripening the fruit, varies in different plants. Most fruits ripen within a year from the expansion of the flower, some come to maturity within a few days, others require months. Certain plants, as some Coniferæ, require more than a year, and in the Metrosideros the fruit remains attached to the branch for several years. The following is a general statement of the usual time required for the maturation of fruits:—

Grasses and Grains13 to 15 days.
Raspberry, Strawberry, Cherry2 months.
Bird-cherry, Lime-tree3 months.
Roses, White Thorn, Horsechestnut4 months.
Vine, Pear, Apple, Walnut, Beech, Plum, Nut, Almond5 to 6 months.
Olive, Savin7 months.
Colchicum, Mistletoe8 to 9 months.
Coniferæ10 to 12 months.
Some Coniferæ, certain Oaks, and Metrosiderosabove 12 months.

"The ripening of fruits may be accelerated by the application of heat, the placing of dark-colored bricks below it, and by removing a ring of bark, so as to lead to an accumulation of sap. It has been observed that plants, subjected to a high temperature, not unfrequently prove abortive; this seems to result from the over stimulation, causing the production of uni-sexual flowers alone. Trees are sometimes made to produce fruit by checking their roots when too luxuriant, and by preventing the excessive development of branches."[22] Here we have the explanation of the processes of root pruning and of summer pinching, and shortening-in, which have been more extensively introduced upon another page; as well as the plan for inducing fruitfulness in such trees as are tardy from excessive wood-growth, by hacking the bark to interrupt the flow of sap from the buds to the roots; by this, some of the former are changed to flower-buds.

We may learn to judge of the condition of ripeness of our larger succulent fruits, such as apples and pears, by a little experience. When ready to be picked, they will have attained their maximum size, their color will have changed somewhat from its greenness, and they will assume a sort of translucency that indicates the approach of maturity; but the best practical test for the fruit-gatherer, is the ready separation of the stem from its attachment. In those fruits, which are suspended by a stem of considerable length, and in which this organ belongs to the fruit itself, and is intimately connected with its tissues, we shall find that it will part easily from the branch at that period of ripeness when it is best to separate it. Such fruits are often much improved by a continuation of the process of ripening after they are gathered, but this more properly belongs to another division of the subject. There is another class of fruits which are found to attain their greatest excellence and most perfect ripening upon the tree itself, and these can never be enjoyed elsewhere in so great perfection as in close proximity to the place of their production; because, so soon as they are separated from their connection with the plant, a process of decomposition commences, they begin to decay, and many of them soon become really unwholesome. Most of those that are called stone-fruits are of this character, such as peaches, nectarines, apricots, plums, and cherries—all of which have a very transitory period of excellence. The same is still more remarkably the case with most of the berries, hence all of these classes of fruits are better adapted to a near than to a distant market.

With apples and pears, however, the case is quite different. Some of these, it is true, especially some of the summer varieties, will attain a perfect state of ripeness while yet attached to the tree, and some of them will even remain hanging to the twig, until they reach that condition of over-ripeness in which they lose a portion of their fine juices and become mealy, or incipient decay may set in, so as to make them rotten at the core. Hence, in nearly all varieties, it is found best to pluck the fruit a little prematurely, and we are guided by the natural indication of the falling of a portion of the crop. By this means we can, in a degree, control the final ripening of our fruits; and we have the great advantage of being able to ship them in a firm condition to distant markets, so as to arrive at the end of a long journey in prime order; whereas, if thoroughly ripe, they could only be transported a few miles, and then needing the greatest care in their handling. Our summer varieties always require to be near their ultimate ripeness when gathered; for, if plucked too soon, they will wither, and be worthless. Among these, there are some varieties, particularly of the apple, which continue ripening for a long period. In the limited family orchard this quality is a great desideratum in the summer fruits, but it is quite otherwise in the orchards, which are planted for profit in the market, because of the increased expense of gathering only a few at a time repeatedly, instead of clearing the tree at once. It is also found to be an advantage in shipping, to have a considerable quantity of a kind to send off at one time.

Gathering.—We now come to the important matter of harvesting our crops of fruits that have been the cause of so much care and anxiety, as well as of pleasure. This will require new considerations as to its disposition and preservation to the best advantage, and will call for a discussion of the best modes of packing, storing, ripening, and transportation to market.