FRUIT, that part of a plant in which the seed or other reproductive element is perfected; in ordinary plants the matured ovary with its pericarp and other parts. Strictly speaking the term is confined to the true seed plants (sper matophytes). This botanical definition is largely extended in popular usage to include the sporangia of mosses and the sori of ferns and still more loosely and erroneously to any plant part useful to man.
Within the limits of the definition fruit structures show exceedingly wide variation. Typically the fruit is a mature ovary which con tains seeds, but in some cases, as in the straw berry, the seeds are practically outside the being embedded in the pulp. Because of the difficulty of making a satisfactory and all-inclusive general classification on any other than that of evolutionary development the fol lowing sketch is given.
Dry Fruits.— Starting with those simplest flowers in which all the carpels (simple pistils. or one of the elements of a compound pistil) are separate, we find the stigina and style usu ally withering back as no longer of service, and the ovary enlarging, as the fertilized ovules grow up into seeds. But in many simple flowers more ovules are produced than are fertilized, and generally also more fertilized than can be developed up to maturity; hence the reduction of the ovules is exceedingly common, as is sim ply exemplified in the horse chestnut.
A second principle of fruit-making is reached through keeping in mind the origin of the ovary from one or more carpellary leaves, of which the individual development has been so greatly checked that they remain closed upon the ovules, and frequently even coalesce with each other from the base upward, so forming a many-celled ovary. Yet the tendency to their individual expansion is not lost; in many mon strosities, and normally in a few types, such as the- common mignonette, the carpellary leaves early begin to expand, so opening the ovary and exposing the seeds long before ripeness. Far more frequently, however, this final develop ment of the carpellary leaves is delayed until the growth-processes of the seed and fruit have ended, and it is, therefore, accompanied, or even receded, by their death; the separation often indicating the lines at once of leaf-margin and leaf-fall.
In the best-developed carpellary leaves, such as those of the more floral Ranunculacece, we naturally find the ovary opening along the line of its united ovule-bearing margins. This is what is termed a follicle.
Since, however, the ovules are on the united margins, the midrib tends to interpose little or no resistance to a tendency to split or tear along its fold. Such '
Another is the siliqua (or when shortened and broadened the silictila) of Crucifera. Here the placental edges of two united carpels de velop a transverse septum which divides the fruit; and this is left when the lobes split away, as so familiarly in honesty.
Among united ovaries which readily split open at the united margins (septicidal) is that of gentian (q.v.), while the more familiar three celled ovary of violet, with its parietal tation, gives a characteristic example of cence along the midribs of the united carpels, so opening the lbculi (loculicidal). In the five-celled capsule of the geranium (q.v.) the carpellary leaves separate not only at the sides but also at the base, so curling inwards and projecting the seed. Where, however, the placenta: remain more or less completely upon a central column from which the valves are tached, the dehiscence is said to be septifragal.
In henbane (Anagallis), etc., the dehiscence is circular (circumscissle). Many-celled cap sules are numerous in which the leaf-opening or dehiscence is greatly reduced from complete ness; witness the valvular and porous dehiscence of the Lychnis and of the poppy respectively. Such cases clearly point us to those of carpels which do not open at all. Such indehiscent fruits, produced from carpels so persistently embryonic, are usually short, few or one-ovuled, and, for the most part, little specialized. Thus the follicle of the Ranunculacecr of more spe cialized floral character becomes shortened into the one-seeded indehiscent achene of the ane mone and the buttercup. In the achene of the grasses (which similarly represents the capsule of the ancestral lilies) the thin dry pericarp becomes inseparable from the seed-coat (hence the term caryopsis) ; in many trees (for exam ple, hazel) it becomes hardened and- thickened as a nut. In composites, too, the achene is practically a nutlet, although often (on account of its being inferior) superfluously termed a cypsela. Less extremely reduced representa tives of the various multicellular ovaries to which such fruits correspond are afforded us by borages or mints in which the two-celled ovary of the primitive solanaceous type be comes, as in thorn-apple, etc., subsequently divided into four parts. In Umbellifera we have another characteristic form of schizocarp, as all such fruits are termed which split up without truly carpellary dehiscence, although the tendency to this can be seen still to have some influence. Here the separate portions (or mericarps), each resembling an achene or nut, are two in number, and when ripe swing off upon the ends of a forked carpophore.