Fleshy So far all our fruits have been dry ; but a different physiological principle of fruit formation is necessary to comprehend those in which the pericarp is succulent. For, just as the effect of fertilization is seen in many animals to extend beyond the mere ovum to the parent organism, and also in many of the lowest plants, so it is in the case before us. Even in fruits which are dry on ripening we have seen that the ovaries or loculi, on which no demand is made for the growth of fertilized ovules, be come reduced or disappear. Sometimes it may be merely the coats of the seed (as in the pome granate) which undergo the complex histologi cal and chemical changes which we sum up as those of succulence and ripening; at other times largely their placentas, as in gooseberry and currant. Yet, as in these, the innermost of the ovary may become succulent as well. In the orange also the seeds are imbedded in the familiar succulent tissue of the enlarged loculi or "cells" of the endocarp; the grape, too,gives a characteristic example of soft endocarp. These may all be classed as berries or baccate fruits, for the distinction of the succulent product of an inferior ovary as a berry, from that of a supe rior one, as a uva or grape, need hardly be al lowed to increase our nomenclature. A pepo is merely a berry in which the epicarp is thick and tough (for example, .a melon, with which the orange and the pomegranate may be reck oned). Where the succulent change, instead of primarily affecting the deeper tissues of the fruit, and so producing a berry, leaves the endo carp hard, we have the drupaceous or stone fruit. The endocarp here forms a more or less complete "stone" or "pit° around the kernel or seed, the difference from an ordinary nut being due to the succulence of an outer layer (meso carp), with a more or less leathery outer skin, the epicarp. The plum, peach and cherry are the most obvious examples; but, since we may have many carpels thus transformed and more or less united as in the raspberry, we may have an aggregate fruit or syncarp of tiny drupes. The walnut and even the coconut are hence not true nuts. (See Nuts). The immature succu lent mesocarp of the former is familiar in pickled walnuts, the ripe walnut we crack being merely the stony endocarp (which is exceptionally spe cialized in being set free by the bursting of the mesocarp on ripening). Coconut fibre is the fibro-vascular tissue of the mesocarp, the fruit being thus broadly comparable to a peach which has wizened while still young and stringy. But,. as in the kindred grass, the coats of the ovule further unite to the endocarp.
The numerous carpels of the strawberry, al though, of course, corresponding to those of the allied raspberry, remain mere nuts; here, how ever, the subjacent portion of the floral axis or receptacle becomes succulent. In the perigy nous and epigynous Rosacecr the same change may take place; hence the rose-hip is a sutcu lent axis, enclosing a multitude of nuts. The apple or upomeo is more akin to the drupe, since the carpels, here deeply sunk in the upgrown floral axis, develop a hard endocarp correspond ing to the stone of a drupe.
Fertilization may even be followed by suc culent or other thickening of the floral enve lopes, or of the floral axis with subjacent bracts — the various cupules, as of acorn, beech, hazel nut, etc., being of this nature. Or we may have a spurious fruit developed at the expense of an entire inflorescence, as in the pineapple, Dor stenia and fig.
' In the plantain and the banana the fruit is fleshy but when normally ripened it dehisces by the splitting of the pencarp into valves somewhat after the order of a bean pod. Another anomaly is the alniond in which the construction is precisely the same as in the peach except that in the former the pericarp is fibrous; in the latter fleshy.
Chemical Composition of Fruits.— Our
knowledge of the chemistry of fruit may be dated from the analyses of Fresenius (1857). But because of the innumerable varieties of almost every cultivated fruit, the effects of different soils and climates upon these, and still more of the fluctuation due to better or worse seasons, the results of any one chemical analysis would tend to convey an idea of undue precision. Thus — for example, while the ratio of sugar to free acid in certain grapes of an Ordinary wine-year was found to be 16 to 1, in a very bad year it sank to 12, and in a very good year rose to 24. Hence a broad outline may be of more general use than the statistics of any one analysts.
The percentage of water may be taken as varying from 78 to 80 in the grape and cherry, as from 82 to 85 in plums, peaches, apples and pears, as 82 to 87 in brambles, currants, etc., and as much as 95 in the watermelon. The proportion of insoluble residue — skin and cel lulose, stone and seed — obviously also varies greatly with succulence and ripeness, but may be taken, one fruit with another, at not less than from 4 to 6 per cent. Unripe fruits may contain a notable proportion of starch, but this is fermented on ripening into glucose and other sugars, fruit-sugar, grape-sugar, cane-sugar or (in Sorbus) sorbin. The only fruits which re tain starch in important quantity are those of the banana, breadfruit-tree and baobab ; hence the exceptioi al nutritive value of these. The olive alone yields a notable proportion of oil. The proportion of sugars varies exceedingly, dates, dry figs "(48 per cent) and raisins (56 per cent), again very important foods, heading the list. Grapes, of course, stand high, from 12 tb 18, indeed sometimes as much as 26 per cent, cherries from 8 to 13, apples 6 to 8, pears 7 to 8, plums 6, red currants 4.75, greengage plum 3.5, peach and apricot only 1.5. The pro portion of pectin bodies is, however, exceed ingly notable, especially in fruits such 'as the three last named. In unripe fruits (as also in roots) we find pectose, a body apparently re lated to cellulose, but easily transmuted by a natural ferment or by boiling with dilute acid into pectin, GM., and its allies. These are all more or less soluble in water, with which they readily form a jelly (whence the peculiar consistency of our fruit-preserves). The pro portion of soluble pectin and gum varies con siderably and is of great importance to the blandness and agreeableness of fruit, the harder and more common apples having con siderably less than 3 per cent and the best reinetts nearly & The red currant, indeed, like berries in general, has exceedingly little (025 per cent) ; while the apricot has as much as 9, the greengage plum 12 and the peach 16 — a circumstance which. explains the peculiarly melting quality of these fruits, especially the last-named. The free acid also vanes greatly, from 2.4 per cent in the red currant, 1.4 in the raspberry, and nearly as much in the sourest cherries, to 0.5 in sweet cherries and a minimum of 0.1 or less in the sweetest pears. That of apples and of grapes, of course, varies greatly, but both may generally be taken at from 0.75 to 1, while the apricot and peach stand at 0.3 or 0.4. The acid is primarily malic, but citric, acetic, oxalic, tannic and others may also be present, The quantity of albuminoids is of course small, in fact, inadequate to render most fruits staple food. Yet it is by no means inappre ciable, ranging from nearly .5 per cent in the majority of fruits to .7 or .8 in the grape (2.7 in raisins), and above 1 in the melon and the tomato. Hence to acquire albuminoids equal to those of one egg we must eat 11/2 pounds of grapes, 2 pounds strawberries, 21/2 pounds apples or 4 pounds pears. To replace 1 pound starch =51/2 pounds potatoes, we need 5.4 pounds grapes, 6.7 of cherries or apples, or 12.3 of strawberries.