This section is from the book "Commercial Gardening Vol1", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
As the result of the fertilization of the egg cell and the production of an embryo, the pistil becomes the young fruit. Usually this includes only the ovary and stigma, with the style if present, as well as the ovules. In those cases where the receptacle grows up around and adheres to the ovary walls, that also forms part of the fruit, as in the Cucumber, Melon, Apple, and Daffodil, with the withered remains of the flower on the top of it. The simplest forms of fruit may be seen in the Buttercup and Strawberry, in which the small, mature fruits resemble seeds. In the Christmas Rose and Columbine it becomes dry, splits along one edge, and is termed a follicle; in the Pea it splits along both edges and is named a legume or pod. The Pansy, Poppy, and Snapdragon have dry seed vessels, opening by valves or pores and named capsules. The fruit of the Gooseberry and Currant is a true berry, because inferior, one-celled, and pulpy. The fruit of the Apple is called a pome.
The inner wall of the ovary becomes bony in the Cherry, Peach, and Plum, while the portion between this and the skin becomes pulpy; the fruit is a drupe (tig. 58). That of the Raspberry and Bramble consists of an aggregation of drupels or small drupes. The Mulberry fruit resembles it, but is made up of a large number of flowers, the perianth of which becomes fleshy, and the fruit is termed a sorosis. This sisterhood of clustered fruits is carried still further in the Pineapple, the flowers, pistils, bracts, and axis forming one pulpy mass. The Fig has a fruit consisting of a whole inflorescence, enclosed in the hollow, pulpy axis, each seed, so-called, being a tiny fruit from the botanist's point of view.
The circumstances which favour the ripening of fruits under glass are a drier atmosphere, plenty of air, and a higher temperature than usual to secure the chemical changes, whereby harsh and acid juices may become pleasant to the palate, and starch and other reserve matters may be converted into sugar. Black grapes require to be shaded by their foliage, and white varieties to be exposed. Cucumbers require a thin shading to prevent the development of too much carbon in them, which means the loss of the green colour. Apples, Pears, Plums, Cherries, Peaches, and Nectarines require full exposure to sunlight to change the chlorophyll granules in the skins into red and yellow ones. Apples and Pears grown in pots take on the brightest and darkest colours if stood out-of-doors to mature.