22. Pyrus L. (pear)

Plants small to medium trees. Branches sometimes producing short, stout branchlets with thorny tips. Bark dark brown to gray, on younger trunks relatively smooth but with prominent, raised branch scars and lenticels, on older trunks developing a network of flat-topped ridges, these breaking up into more or less rectangular, fine, scaly plates. Winter buds ovoid, with several overlapping scales. Leaves alternate but often appearing clustered at the tips of short branchlets, rolled during development, long-petiolate, the petioles lacking glands. Stipules small, membranous to papery, shed early. Leaf blades simple, unlobed, broadly ovate, broadly elliptic, or broadly oblong-obovate to nearly circular, mostly rounded at the base, tapered to a sharply pointed tip, the margins finely, evenly, and bluntly toothed, the surfaces cottony-to cobwebby-hairy during development, glabrous at maturity, the upper surface lacking glands, often shiny. Inflorescences terminal on main branchlets or more commonly on lateral, short branchlets, dome-shaped clusters (often with a short central axis and thus technically racemose) of 4–12, long-stalked flowers, produced before or as the leaves uncurl, the axis and stalks glabrous or hairy, the stalks each with a small bract at the base, this linear to narrowly oblong-elliptic, brown to reddish brown, hairy, mostly shed early. Flowers epigynous, usually strongly malodorous, the hypanthium fused to the ovaries, cup-shaped to more or less urn-shaped, with a free, thickened rim nearly closing the tip, glabrous or hairy. Sepals 5, spreading to somewhat reflexed at flowering, lanceolate-triangular to lanceolate, long-tapered to a sharply pointed tip, the margins and/or upper surface hairy, sometimes persistent at fruiting. Petals 5 (except in rare doubled forms), broadly obovate to nearly circular, white, occasionally tinged with pink. Stamens usually (15–)20, the anthers pink to red. Pistil 1 per flower, of 2–5 fused carpels. Ovary inferior, with 2–5 locules, each with 2 ovules. Styles 2–5, free, protruding from the rim of the hypanthium the stigmas more or less capitate. Fruits pomes, globose to obovoid or pear-shaped, glabrous at maturity, variously colored, the surface often with small, light or dark dots, with 4–10 more or less easily exposed seeds embedded in the “core” of leathery to papery carpel wall remains and the fleshy portion, this with abundant stone cells (creating a gritty texture). Seeds more or less obovoid, the outer surface smooth, dark brown to black About 25 species, Europe, Asia, Africa, introduced widely.

The present treatment follows a relatively restricted concept of Pyrus, in contrast to the much broader circumscription favored by Steyermark (1963) and K. R. Robertson (1974), which includes species here segregated into such genera as Aronia and Malus. Morphologically, Pyrus in the strict sense is distinctive mainly in the relatively cryptic anatomical feature of stone cells (sclereids) in its fruits (which give the flesh a gritty texture in fruits of edible species), which are shared with the genus of quince, Cydonia Mill. (Aldasoro et al., 1998). Evidence from details of floral morphology (Rohrer et al., 1994) and phytochemical data (A. H. Williams, 1982) support the splitting of the two genera. Molecular studies (C. S. Campbell et al., 2007; Potter et al., 2007) also have tended to reinforce Pyrus as a natural genus and to suggest that some of the other segregates of Pyrus are more closely related to other genera. It should be noted that even with analysis of massive molecular data sets, the phylogenetic relationships among Pyrus and related genera still are not fully understood (C. S. Campbell et al., 2007).