This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Trees, or some species shrubs, with simple leaves. Flowers large, showy, white or pink, in simple terminal cymes. Calyx urn-shaped, 5-lobed, the lobes acute. Hypanthium nearly closed by a disc-like cushion. Petals 5, rounded, short-clawed. Stamens usually numerous; styles mostly 5, distinct, or united only at the very base; ovules 2 in each cavity; carpels cartilaginous or leathery. Fruit a pome, usually pear-shaped, its flesh abounding in grit-cells. [Latin name of the pear.]
About 12 species, natives of the Old World, the following typical.
Pyrus communis L. Sp. Pl. 479. 1753.
A tree, sometimes 60° high and with a trunk 2°-3° in diameter, commonly much smaller, the branches usually thorny. Leaves ovate, elliptic or obovate, finely serrulate or entire, slender-petioled, 1 1/2'-3' long, downy and ciliate when young, becoming glabrous or nearly so when old, the apex acute or acuminate, the base usually rounded; petioles sometimes as long as the blades or longer; cymes few-several-flowered, borne at the ends of short twigs of the preceding year; pedicels 9"-2' long, at first downy; flowers white, 1'-2' broad; calyx-lobes about as long as the tube; styles distinct to the base; pome, in the wild form, seldom over 2' long, in the numerous cultivated forms often much larger.
In thickets and woods, Maine to New York, New Jersey and Pennsylvania, escaped from cultivation. Native of Europe and Asia. Wood hard, fine-grained, reddish-brown; weight per cubic foot 51 lbs. April-May.
3. M└LUS Mill. Gard. Dict. Abr. Ed. 4. 1754.
Trees or shrubs, with alternate toothed or lobed leaves, and showy pink or white flowers in simple terminal cymes. Calyx-tube urn-shaped or campanulate, 5-lobed. Hypanthium open, not closed by a cushion. Petals 5, rounded, clawed. Styles 2-5 (usually 5), united at the base; ovules 2 in each cavity, carpels papery or leathery. Fruit a pome, usually depressed-globose, mostly hollowed at the base, but sometimes rounded, its flesh not containing grit-cells. [Greek, apple.]
About 15 species, natives of the north temperate zone. Besides the following, another occurs in northwestern America. Type species: Pyrus Malus L.
Leaves glabrous, at least when mature.
Leaves ovate-lanceolate to oblong, narrowed at the base.
Leaves obtusish or acute.
Leaves ovate, cordate or rounded at the base.
Leaves persistently pubescent or tomentose beneath.
Leaves mostly narrowed at the base; pome l'-1 1/2' in diameter.
Leaves rounded or subcordate at the base; pome 2'-4' in diameter.