FRUIT, Fructus, in the botanical use of the term, in phanerogamous plants, is a mature ovary containing a seed or seeds; and in cryptogamous plants, a spore-case (sporangium or theca) containing spores. Other parts of the flower, most frequently the calyx, sometimes remain after flowering is over, undergo a further development, become incorporated with the ovary, and form part of the fruit. The development of the F. in phanerogamous plants depends upon the fertilization of the ovules, and when this has not taken place, the flow of sap to the ovary usually soon ceases, and it drops off with all the other remains of the flower; although there arc exceptional cases of seedless fruits, as seedless oranges, bananas, grapes, bayberries, etc., in which, how ever, it may be supposed that fertilization takes place, and that unknown causes after wards operate to prevent the development of the seed, and to direct the flow of sap more exclusively to the nourishment of the succulent parts, which are thus increased and improved. This supposition is rendered more probable by the circumstance that time production of seedless fruits appears to be at least sometimes a consequemo of age and diminished vigor in trees.
The F., like the ovary, may be composed of one carpel, or of more than one. But the F. sometimes differs from the ovary, through the development of some of the parts, and the non-development or obliteration of others; so that an ovary with several cells may be converted into a one-celled F.; and of several ovules, all but one may become abortive, so as to produce a one-seeded fruit. Thus the three-celled ovary of the oak and of the hazel, with two ovules in each cell, becomes, by the non-development of two cells and five ovules, a fruit with one seed; and the two-celled ovary of the ash, and the three-celled ovary of the cocoa-nut, likewise produce one-celled and one-seeded fruits. Sometimes also false dissepiments are formed, which produce in the F. a greater num ber of cells than existed in the ovary. More generally, however, the F. agrees'with the ovary in the number of its cells and seeds. But not unfrequently, the structure of the F. is rendered comparatively difficult to determine, through the development of succu lent matter or pulp, sometimes in one part and sometimes in another.
All that is external to the proper integuments of the seed in the ripe F. is called the pericaiT (Gr. pen, around; and karpos, fruit); and this, which varies extremely in size and other characters, usually consists of three layers, the outermost of which is called the epicarp (Gr. epi, upon); the middle one, the mesocarp (Gr. mesos, middle), or sometimes the sarcoca7p (Gr. RarX, flesh); and the innermost, the endocarp (Gr. endon, within). These
parts exhibit great variety, but it is generally the mesocarp which becomes succulent or fleshy, as in the peach, cherry, plum, and other drupes; and in the pear, apple, and other ponies. In drupes, or stone-fruits, the endocarp is the hard shell which imme diately covers the seed; in pomes, it is the scaly lining of the seed-bearing cavities in the center; in both drupes and pomes, the epicarp is the outer skin. So in melons, cucumbers, and gourds, the succulent part is the mesocarp, greatly developed, with a thin epicarp and a thinner endocarp. In the orange, however, and all of that family, the epicarp and mesocarp together form the whilst- the pulpy cells belong to the endocarp, In berries, as the gooseberry, grape, etc., the pulpy matter does not belong to any of the layers of the pericarp, hut is formed from the placentas of the seeds.
When the fruit, as the fully developed ovary, is considered as a modified leaf or leaves, the epicarp is viewed as representing the epidermis of the lower surface, the endocrap the epidermis of the upper surface, and the rnesocarp the substance (paren chyma) of the leaf. The midrib of the leaf is traced in the dorsal suture of the fruit or of each component carpel, and the ventral suture is formed by its folding together' and the conjunction of its edges. The dorsal it nd ventral sutures are very obvious iu the pods of pease, beans, etc.; and even in fruits formed of several carpels intimately com bined, they often become very apparent when the ripened fruit opens to allow the escape of the seeds. The opening or dehiscence (Lat. dehisce, to open) of fruits takes place in various ways; thus, the fuit sometimes resolves itself into its original carpels by- separation through the dissepiments, which divide into two plates forming the sides of the valves, and the carpels further open by their sutures; the pericarp sometimes splits at once by the dorsal sutures of the carpels; sometimes it divides transversely, and throws off a lid; sometimes it opens more partially by pores, etc. Many fruits, however, are indehiscent, some of which are fruits having a very hard pericarp, as nuts, and some are fruits having a soft pericarp and much pulp. The decay of the peri carp is in these cases necessary to the liberation of the seeds, unless when this is accom plished by such means as the fruit becoming the food of animals, by which also the seed§of plants are often widely distributed. ''The decay of the pericarp seems intended, in mNy cases, to provide the first nourishment for the young plants which spring from the seeds.