iq-ATIVE AMERICAN SPECIES OF PEUNUS. 21 



20. Petioles 5 to 10 mm. long, leaves 3.5 to 7 cm. long, obtuse or 

 sometimes acute at the apex. Fruit about 10 to 15 mm. in 

 diameter. Eastern and northern species P. cuneata. 



20. Petioles 5 to 6 mm. long, leaves 3 to 4.5 cm. long, acute or rai'ely 

 obtuse at the apex. Fruit about 15 to 18 mm. in diameter. 

 Western species P. besseyi. 



DESCRIPTIONS OF THE SPECIES AND THEIR HYBRIDS. 



Prunus Nigra Ait. 



(Canada plum.) 



Prunus nigra Aiton, 1789, Hort. Kew., v. 2, p. 165. 



Prunus borealis Poir., 1804, in Lam. EncycL, t. 6, p. 674. 



Prunus mollis Torr., 1824, Fl. North and Mid. U. S., v. 1, p. 47*0. 



Prunus americana nigra Waugh, 1896, in Vt. Agi-. Exp. Sta. Bui. 53, p. 58. 



Cerasiisborealismchx., 1803, ? Fl. Bor. Amer., t. 1, p. 286. 



Cerasus nigra Lois., 1812, Nouv. Duham., v. 5, p. 32. 



Leaves (PI. I, fig. 2) oval or obovate, mostly 8 to 13 cm. long, 4.5 to 

 7 cm. broad, rounded at the base, abruptly acuminate toward the 

 apex, green and glabrous above, or with scattered hairs along the 

 veins, pale and becoming glabrous below except along the midvein 

 and in the axils of the lateral veins, or sometimes with scattered hairs 

 along the lateral veins, when young usually somewhat pubescent 

 above and rather strongly so below, rarely entirely glabrous, the 

 margins rather coarsely and unevenly serrate, the serrations rounded 

 and in the young leaves glandular, the glands usually remaining as 

 small callous points; petioles 10 to 18 mm. long, pubescent on the 

 upper surface with longish hairs, or sometimes entirely glabrous, 

 glands one to three near the apex or often entirely absent; stipules 

 linear or sometimes lobed, the margins glandular. Flowers 2 to 2.5 

 or sometimes even 3 cm. broad, appearing before the leaves from the 

 last of April in the southern portion of its range to the last of May in 

 northern locahties; umbels nearly sessile, mostly 2 or 3 flowered; 

 pedicels 10 to 20 mm. long, usually about 18 mm., glabrous or very 

 rarely finely pubescent in some western material; calyx usually 

 somewhat reddish, in age frequently conspicuously so, the tube rather 

 narrowly obconic, about 3.5 to 4 mm. long, or in cultivated trees the 

 tube and lobes sometimes each 5 mm. long, glabrous, calyx lobes 

 oblong-ovate or oblong-obtuse, glandular serrate, glabrous or rarely 

 pubescent on the inner surface mainly toward the base, and still 

 more rarely with a f(;w scattered hairs on the outer surface, the lol)es 

 at Icngtii spreading or refiexed; petals white or in age with a decided 

 tinge of pink, oblong-ovate to nearly orbicular and abruptly con- 

 tra<;ted to a claw, 10 to 12 mm, long, to 10 mm. broad, usually erosci 

 toward the, apex, sometimes consj)icuously so. Fruit oblong-oval, 

 2.5 to 3 ciri. long, 1,8 to 2.5 cm. in diameter, orange red or sometimes 

 d''«-[) rciirisoti, varying to orange y<'llow, nciu'ly (l<'.Htitut<i of bloom, 



