10 THE PLUMS OF NEW YORK. 



D.D. Flowers mostly single. 



E. Leaves small, less than 2 inches in length; 



sometimes a tree; very thomy 3- P- spinosa. 



E.E. Leaves large, more than 2j inches in . 



length ; a shrub ; thorns few 4. P. curdica. 



C.C. Shoots glabrous or soon becoming so, pedicels glabrous. 



D. Pedicels shorter than the calyx-cup; leaves glabrous 



or sparsely pubescent on the under side along the 



rib ; flowers in pairs 5- P- tocomilia. 



D.D. Pedicels more than twice as long as the calyx-cup. 



E. Flowers mostly single; leaves hairy along the 



midrib on the under side; petiole J as long 



as the leaf-blade; a tree 6. P. cerasifera. 



E.E. Flowers in threes; leaves glabrous, petiole 

 shining, leaf-margins finely and closely serrate, 

 teeth glandular-pointed; stamens about 25 .... 7. P. monticola. 

 E.E.E. Flowers in threes; leaves glabrous, often 

 shining, leaf-margins finely and closely serrate, 

 teeth glandular-pointed; stamens about 25. .. 8. P. triflora. 

 B.B. Leaves upright, peach-like, glabrous, veins very conspicuous, 

 under side barbate at axils of veins; separated from all other plums 

 by the leaf-characters and by the large, flattened, brick-red fruits 9. P. simonii. 

 A.A. Flowers in clusters of 3 or more, rarely 2. American plums. 

 B. Plants trees. (P. angtistifolia rarely a tree.) 

 C. Leaves broad, mostly ovate or obovate. 

 D. Leaves long-ovate or long-obovate. 

 E. Flowers white. 



F. Leaf -serrations glandless, acute; petiole 

 usually glandless; calyx-lobes 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-cre- 

 nate; 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, glan- 

 dular only when young; petioles bi- 

 glandular; 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, glandu- 

 lar-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. 



