Nearly every botanist who has attempted to classify plants has grouped the pome-fruits according to a plan of his own. There are, therefore, several classifications of genera and species of the pomes, in consequence of which the nomenclature is badly confused. A century ago the tendency was for botanists to put in the genus Pyrus the apple, pear, crab-apple, quince, medlar, sorbus, and chokeberry. The modern tendency is to segregate these fruits in distinct genera in accordance with common names. As a rule the differences which suggest a distinct common name suffice for a botanical division.
The pear and apple, however, are usually kept together in Pyrus, and botanists generally agree that separation in species is sufficient, or, at most, that the separation should not be greater than in two sections of the genus. Happily, the difficulties of classification in botany trouble little or not at all in pomology, as each of the pome-fruits constitutes a distinct pomological group. The distinguishing characters of Pyrus are:
Woody plants, trees or shrubs, with smooth or scaly bark. Leaves simple, or sometimes lobed, alternate, usually serrate, deciduous, with deciduous stipules which are free from the petiole. Flowers perfect, regular, borne in compound terminal cymes; torus urn-shaped, adnate to the ovary and inclosing it with thick, succulent flesh at maturity; calyx-lobes 5, acuminate and reflexed, persistent in some and deciduous in other species; petals 5, white, pink or red, inserted on the thickened border of the disk; stamens 15 to 20, in three rows; styles 2 to 5, free or united below; carpels 2 to 5, inferior, crowned by the styles, usually 2-seeded. Fruit an ovoid or pyriform pome; seeds two in each cell, brown or brownish, lustrous, mucilaginous on the outer surface.
The genus comprises fifty to sixty species in the north temperate zone of the three continents. The largest number is found in south-central and eastern Asia. In North America, Pyrus is represented by five species, while eight or nine species inhabit Europe. In several of the species there are many natural varieties. The two sections of Pyrus, given the rank of genera by some authors, are distinguished as follows:
1. Apples (Malus). Flowers pink, rose-color, red or sometimes white, borne in fascicles or subumbellate clusters on short spurs or lateral branchlets; ovary 3- to 5-celled; styles more or less united at the base. Fruit more or less globular with a distinct depression at both ends, the flesh without grit cells, rounded at the base. The species in this section number 30 to 40, of which not more than a half dozen are domesticated.
2. Pears (Pyrus). Flowers white, few, borne in corymbs on short spurs or lateral branchlets; ovary 5-celled; styles usually free. Fruit usually pyriform, sometimes subglobose, usually conical at the base, the flesh usually bearing grit cells when ripened on the tree. The species number 15 to 20 of which but two are truly domesticated, but several others give promise of value for stocks and possibly for their fruits.
THE STRUCTURAL BOTANY OF THE PEAR
A major purpose in The Pears of New York is to describe varieties of pears so that their faults and merits can be seen, and that varieties may be identified. It is apparent at once that one cannot describe accurately nor understand the descriptions of others unless acquainted with the organs of tree and fruit—one must know the form and structure of the whole plant. A study of the organs of plants is structural botany. Plant descriptions are portraitures of the plant’s organs, and structural botany thus becomes the foundation of systematic pomology, with a study of which, as concerns the pear, we are to be chiefly concerned in the following pages. We must, therefore, pay some attention to the structural botany of the pear. A pear is one of the pome-fruits. What is a pome?
A pome is variously defined by students of structural botany. The most conspicuous part of the apple, pear, or quince, the best-known pome-fruits, is the outer, fleshy, edible part. This succulent part is said by some botanists to be the thickened calyx; others say that it is the enlarged receptacle. Some botanists believe that a pome consists of two to five drupe-like fruits, each drupe called a carpel, each of which contains one or more seeds. These drupes, if they are rightly so-named, are held together by a fleshy receptacle. The best definition seems to be that a pome is a fleshy fruit of which the compound ovary is borne within and connected to the receptacle.