entire, glabrous on the outer, pubescent on the inner surface; stamens about 30; stone turgid, large, pointed at the apex =10. P. americana.= F.F. Leaf-serrations glandular, wavy-crenate; petioles glandular; calyx-lobes glandular-serrate, pubescent on the inner surface; stamens about 20; stone turgid, small, prolonged at the ends =11. P. hortulana.= E.E. Flowers fading to pink. F. Leaf-serrations coarse, rounded, glandular only when young; petioles biglandular; calyx-lobes glandular-serrate, not pubescent on the inner surface; stamens about 30; fruit red; bloom light; stone flat =12. P. nigra.= F.F. Leaf-serrations fine, acute, glandular-pointed; petioles biglandular; calyx-lobes entire, pubescent on the outer, tomentose on the inner surface; fruits dark purple; bloom heavy; stone turgid, acute at the ends =13. P. alleghaniensis.= D.D. Leaves round-ovate, obtusely, sometimes doubly serrate; petioles glandless; calyx-lobes pubescent on both surfaces; fruit dark red or purplish; stone turgid, pointed at both ends =14. P. subcordata.= C.C. Leaves narrow, lanceolate-ovate. D. Leaves flat. E. Leaves glabrous; fruits globular, usually purple at maturity but sometimes red or orange-red; bloom thin; stone turgid, cherry-like =15. P. umbellata.= E.E. Leaves pubescent. F. Stone acute at both ends; fruit purple. =16. P. mitis.= F.F. Stone rounded at base; fruits variously colored =17. P. tarda.= D.D. Leaves more or less folded upward. E. Fruits small, ½ inch in diameter, cherry-like; leaves lanceolate, upper surface glabrous, lustrous, lower surface pubescent in axils of veins, marginal teeth glandless; petioles biglandular; stone small, ovoid, turgid, cherry-like; rarely a tree; tender in New York =18. P. angustifolia.= E.E. Fruits large, an inch in diameter, plum-like; leaves lanceolate, peach-like, upper surface glabrous, lower surface pubescent along the midrib; petioles with from 1 to 6 glands; stone compressed and pointed at both ends; usually a tree; hardy in New York =19. P. munsoniana= B.B. Plants shrubs.