53. ROSACEAE 1 25 



7. Pedicels 8-14 mm lona^, srlabrous; fruit 6-7 mm 



s? to' 



m 



diameter; wet woods or in bogs, n. 111. Apr. Wild 



Red Cherry P. pennsylvanica L.f. 



6. Leaves o\ate to siiborbicular, apiculate, crenate, glan- 

 dular between the teeth; fruit ovoid, black or nearly 

 so, 7-10 mm long; roadsides, occasionally escaped 

 from cult.; introd. from Eur. May. Mahaleb Cherry 



P. mahaleb L. 



5. Dwarf shrubs; leaves oblanceolate, acute, serrate except 

 toward the cuneate base; fruit nearly globose, black, 

 acid, 1-1.5 cm in diameter at maturity; sandy soil, n. 111. 



Apr.-May. Sand Cherry P. pumila L. 



4. Flowers larger, the petals 6-16 mm long. 



8. Leaves serrate, the sharp teeth not ending in a gland; petals 



7-10 mm long; calyx-lobes not glandular-serrate. 



9. Petioles glabrous beneath; lower surface of mature blades 



glabrous except along the veins; young twigs glabrous; 



borders of woods, common. Apr.-May. Wild Plum 



--- P. amcricana Marsh. 



9. Petioles pubescent all around; blades usually more or less 



softly pubescent beneath; young twigs puberulent; 



woods and roadsides, common. Apr.-May. [P. ameri- 



cana var. juollis T. & G.] 



- P. lanata (Sudw. ) Mack. & Bush 



8. Leaves crenate-serrate, the teeth ending in a gland ; calyx- 

 lobes more or less glandidar-serrulate; petioles glabrous 

 beneath; twigs glabrous. 



10. Petals 12-15 mm long; leaves broadly obovate or oval; 



river banks, woods, and thickets, not common ; ex- 

 tending southward to Pike Co. May. Canada Plum 



P. nigra Ait. 



10. Petals 6-8 mm long. 



11. Leaves thickish at maturity, narrowly obovate to 

 elliptical, aciuninate, irregularly serrate, glossy 

 above, conspicuously veiny beneath ; flowers open- 

 ing when the leaves are half grown ; roadsides and 

 edges of woods, common. Apr.-May. Hortulan 



Plum P. hortulana Bailey 



1 1 . Leaves thinner, elliptic-lanceolate, acute, finely and 

 evenly glandular-serrate, the veins not conspicu- 

 ous beneath; flowers opening before the leaves 

 have expanded; borders of woods, s. 111., extend- 

 ing northward to St. Clair and Crawford counties. 



Apr.-May. Wild Goose Plum 



P. munsoniana Wight & Hedr. 



3. Flowers several to many, in elongate racemes. 



12. Leaves thin, obovate, sharply serrate with erect or spreading 

 teeth; sepals nearly orbicular, glandular-serrate, decidu- 



