docarp is embedded in the mesocarp, fused with and completely enveloped by the enlarged fleshy recep-
tacle or the fused base of the sepals; the ripened ovary is only a small part of the total structure [1].
By far, the best known and most widely grown pome fruit is the apple (Malus sylvestris). Its flower
parts are in fives: five sepals, five petals, five stamens, and five carpels making up the deeply embedded
ovary (Figure 2). The parenchyma of the fused bases of the calyx, corolla, and stamens constitutes the ma-
jor portion of the edible tissue of the mature fruit. The nonedible core is largely ovary tissue.
Although parthenocarpy is not unknown in some obscure varieties, fruit development normally starts
at pollination. Because most apple varieties are self-infertile, pollen usually has to come from some other
variety (cultivar). Fruit development is almost invariably dependent on fertilization and resultant seed for-
mation. (Fortunately, the buying public’s prejudice against seedy fruits does not include apples.) The hor-
monal control of fruit development was first indicated by the common observation that when seeds fail to
develop in one or more of the five carpels, the fruit tends to grow lopsided. Most flowers never survive
to form fruits. Only about 2 to 4% of the flowers in a normal bloom need to develop to provide as heavy
a crop as the trees can bear.
The epidermis of the very young fruit is constantly growing, initially with very active cell division.
After 4 or 5 weeks of development, cell division slows down and then ceases. As the fruit continues to
expand, the epidermal cells flatten and elongate. As the fruit matures, these epidermal cells become sur-
rounded by cuticle. The cuticle is covered by a layer of wax that is continuous in varieties with a natural
shine but is deposited as irregular platelets in “nonshiny” varieties such as Golden Delicious and Grimes
Golden. Today, most apples are artificially waxed, partly to retard shrinkage, but more because of the
buying public’s fascination with shine (even for fruits that are not naturally shiny). The edible parenchy-
148 GRIERSONFigure 2 Development of the apple fruit from the flower stage. (From Ref. 37.)