The peaches of New York

by U. P. Hedrick

The structure of the glands shows that they are true glands, having an upper layer of long, rectangular, secretory cells that produce a sweet substance, the function of which is not apparent. After the glands have ceased secreting they begin to decay, becoming brown on the upper surface and slowly disappearing until almost nothing is left. This decaying is a very complicated process, being preceded in every case by a suberization and thickening of the cell walls.

"The spines of the leaf are very similar to the glands in structure, having the same upper layer of long cells, but with much more heavily cutinized walls. A study of the transitional forms indicates that the glands are merely modified leaf spines.

The leaves with reniform glands are apparently the highest type and the glandless leaves the lowest, with the transition through the globose type. In support of this view is the fact that whenever typically glandless leaves become possessed of glands they are always of the globose type.

The serrations of the glandless leaves are very strikingly different from those on a leaf with glands. The former leaves are deeply and doubly serrate, while the margins of the latter are always single and crenate. Almost invariably, when glands develop on a normally glandless leaf, the serrations are transformed to crenations, indicating that there is a very close correlation between the glands and the crenations on the edges of the leaves."

The French pomologists, Poiteau and Turpin,[165] seem to have first made note of the glands in describing peaches, recording their discovery by M. Desprez in the nurseries at the Luxembourg in 1810, after which, for a half-century, French, English and German pomologists regarded them as an infallible means of distinguishing varieties. But, by the middle of the Nineteenth Century, classifiers began to give them up because of their variability on leaves of trees of the same variety or even on the same tree. Even Darwin made note of their insufficiency in taxonomic work.[166] Now, no one familiar with any considerable number of varieties of peaches would attach very great importance to glands in a system of classification.

The flowers of peaches are very characteristic, helping to delineate the groups in the several classificatory schemes of various pomologists and being ample to identify not a few varieties. Peach-flowers differ in time of appearance; in length of blooming-season; they may be large, medium or small; pink, rose and rarely white; borne on pedicels of varying length, thickness, color and pubescence; and both the floral and reproductive organs have modifications of their several structures. The size, color and shape of peach-flowers are well shown in the first six color-plates. In some species of Prunus, as some of the plums, the reproductive organs differ greatly in ability to perform their functions, but the blossoms of edible peaches are seemingly always self-fertile and there are less often the mal-formations found in the reproductive organs of some plums.

A well-marked correlation[167] between the color in the inside of the calyx-cup and the color of the flesh of the fruit is one of the distinguishing features of peaches. Yellow-fleshed peaches develop from blossoms in which the inside color of the calyx-cup is orange; white-fleshed peaches develop from those in which the color is greenish or greenish-yellow sometimes approaching a very light orange easily distinguished from the dark orange of the other group. Since the discovery of this correlation in the Station orchards by Mr. Charles Tubergen it has been in yearly use and has enabled us to tell a year or two in advance the flesh-color of seedling peaches, since the first peach-blossoms seldom set fruit.

The fruits, however, furnish by far the best characters upon which to found a classification of peaches. The simplest classification of peaches begins by separating them into smooth-skinned and pubescent sorts; each of these divisions is redivided into clingstones and freestones; these four groups may then be separated into yellow-fleshed, white-fleshed and red-fleshed peaches; still further, most, not all, of the twelve groups made in the first three divisions, separate into round, flat or beaked peaches. These are the major characters of the fruits, little influenced by cultivation or environment, after which there are many minor characters such as size, shape, color, quality and season, all very responsive to changed conditions, that help to describe definitely the many varieties of Prunus persica. The most variable of the minor characters is shape, all peaches tending to lose rotundity in southern climates and to become oblong and beaked. The length and quantity of the pubescence on peaches vary considerably in different soils—the warmer and lighter the soil, the less pubescence. The skin adheres closely to the flesh in some varieties; in others it is non-adherent.

The characters found in the stones of the many species of Prunus are of great value in determining species but they help but little in determining the horticultural varieties of any one species. The stones of the peach do vary, however, very materially in size, shape, grooves and ridges, pitting and in characteristics at base and apex. The color-plates in this text illustrate these differences very well. One may generalize and say that the stones of the freestones are more deeply furrowed and that the sides are smoother than in the clingstones.

The characters of the peach are set forth on the opposite page by reproducing a description as made at this Station in describing a variety for The Peaches of New York. Such a description is, however, but a skeleton, as dead as dry bones, unless a living picture of the variety be made by filling out and covering the skeleton with ample remarks made as the describer studies the plant in the field.