A classification of the different kinds of fruits is extremely difficult, although they afford characters of great importance in descriptive and systematic botany. A conve nient primary division of fruits is into those which are formed from one flower, and those which are formed by incorporation of the ovaries of many flowers. Fruits formed from one flower, by far the most numerous of these two classes, are divided into apo carpous and syncarpous, or into aggregate, and ijncarpous. Apocarpous fruits are formed of one carpel, and are either dry or succulent, dehiscent or indehis cent, one-seeded or many-seeded. Aggregate fruits, sometimes included among the apocarpous, arc formed of several or many free carpels; sometimes dry, sometimes suc culent; sometimes arranged on a convex or elevated receptacle; which becomes succu lent in the strawberry, and constitutes the edible part of the F.; sometimes within a concave receptacle covered by the enlarged tube of the calyx, as in the rose. Syncar pous fruits are formed of several carpels, intimately united in their mature state, so as to form a berry, capsule, pome, silique, etc. Syncarpous fruits sometimes so completely resolve themselves into their original carpels, that these may be regarded as becoming separate achenia. Fruits formed by incorporation of the ovaries of many flowers (collective or anthocarpous fruits) are sometimes dry, as the cones of firs; sometimes succulent, as the pine-apple, the mulberry, and the fig. For further notice of different kinds of fruits, we must refer to particular articles in which they are described, as achenium, berry, capsule, drupe, nut, pome, pod, silique, etc., and to articles on the plants which produce them.
A few plants, particularly the caniferm and cycadacea, produce seeds really naked or destitute of pericarp. Many other seeds were formerly often described as naked, in which the pericarp exists intimately incorporated with the seed, as the seeds of grasses, boraginex, labiate, umbellifera, etc. The real nature is often made apparent by some trace of the style.
The production of ripe F. is exhaustive to the energies of a plant, and plants ordi narily annual may be preserved in life for several years by preventing it. Very young fruit-trees generally fail to bring F. to perfection, and the first flowers of melons and gourds are often, for a similar reason, abortive; whilst, on the contrary, any circum stance that favors an accumulation of sap in a particular season, tends to render fruit trees untisually productive in the next, as when the whole blossoms of a year are killed by frost, or when, from the coldness of the previous summer, flower-buds have not been formed in abundance. Whilst the vital energies of a plant are directed mainly towards the increase of its size, flower-buds are sparingly formed or not at all, as is often the case with fruit-trees growing very luxuriantly, and various modes are adopted to cause the production of flower-buds and of fruit by checking this luxuriance of growth, as by root-pruning, by cutting into the stem of wall-trees to a moderate depth, or by taking off portions of the bark of the stem. Grafting (q.v.) is also of use in this respect.
as well as for the propagation of improved varieties of fruit-trees, the qualities of which would, in all probability, not be found exactly the same in their offspring by seed.
In a very immature state, fruits are in general green and soft, and decompose carbonic acid gas in the sunlight, absorbing the carbon, and setting free the oxygen, like leaves and other green parts of plants. As they advance towards maturity, sonic of them become externally dry and hard, and cease to perform by their surface these functions of vegetation; others, as they become more succulent, change their color, and instead of absorbing carbon and liberating oxygen, absorb oxygen from the atmosphere, and exhale carbonic acid_ c - by Microsoft It would not be easy to enumerate the peculiar substances which are produced in fruits. Different parts of the same F. are often extremely different from one another, as the milk and the kernel of the cocoa-nut, its hard shell, and its fibrous husk. Seeds are indeed generally very different in all their qualities from the pericarp or the pulp by which they are surrounded, and the integuments of the seed often not less dif ferent from the embryo, of all which a ready illustration may be found in the apple or the grape. The most different chemical products of vegetation are sometimes to be found in different parts of the same F., giying them the most varied qualities, as wholesome and poisonous; the succulent part of the F., from the kernel of which strychnia is obtained, is said to be harmless, and the seeds of plums contain so much hydrocyanic acid, that to eat many of them would be dangerous; the capsule of the poppy yields opium, but its se6d contains nothing of the kind, and is bland and nutri tious, abounding in a wholesome fixed oil. The value of fruits to man—which may safely be asserted to exceed that of all other parts of plants—sometimes, as in the corn plants, chiefly depends on the farinaceous matter of their seeds, containing starch, glu ten, etc.; sometimes, as in the banana and bread-fruit, on the starchy matter of the pulpy part; sometimes, as in nuts, on fixed oils; sometimes, as in many succulent fruits, on sugar and various acids, with gum, pectine, etc. Other fruits, or parts of the same fruits, are valuable for the volatile oils which they yield, and. for peculiar principles capable 'of application to medicinal and other uses, or. making them capable of being used as condiments, perfumes, etc. Coffee, cocoa, pepper, vanilla, and many other articles of commerce, are obtained from fruits.