NATIVE AMEEICAN" SPECIES OF PRUNUS, 19 



3. Serrations of the leaves rounded or obtuse (sometimes appar- 

 ently acute by the presence of a pointed gland, rai-ely acute 

 in P. subcordata Pacific coast species with incisely serrate 

 leaves, and in P. orthosepala with glabrous leaves), mostly 

 glandular, at least when they first unfold. Floweis with 

 glandular calyx lobes, except in P. orthosepala and P. angusti- 

 folia, species in which the calyx lobes are merely ciliate, and in 

 P . venulosa ivitJi flowers only 6 to 7 mm. broad 4. 



3. Sen-ations of the leaves pointed or acute, the teeth mostly not 



gland tipped when the leaves unfold. Floioers with calyx 

 lobes eglandular except sometimes inconspicuously glandular 

 in P. americana 5. 



4. Leaves broadly oblong-ovate to slightly obovate, not at all 



trough shaped, the margin often doubly serrate. Flowers 2 

 to 2.5 cm. broad, the calyx usually with a reddish tinge, at least 

 in age, the lobes lanceolate, conspicuously glandular-serrate P. nigra. 



4. Leaves ovate, ovate-lanceolate, oblong-lanceolate or sometimes 



oblong-oval (often orbicular in P. subcordata, Pacific coast 

 species) the margin rarely doubly serrate. Flowers 8 to 15 

 mm. broad, xoith calyx rarely or only slightly reddish, the lobes 

 oblong-ovate, entire, glandular or eglandular 7 . 



5. Leaves rather abruptly acuminate, the margins rather coarsely 



and deeply serrate. Flowers 18 to 25 mm. broad. Fruit red 

 or reddish yellow , 18 to 30 mm. in diameter 6. 



5. Leaves gradually acuminate or merely acute, the margins rather 



finely serrate. Flowers 6 to 14 mm. broad. Fruit purple or 

 more rarely red or yellow, about 15 mm. or less in diameter. . 14. 



6. Tree sprouting from the roots and forming thickets, bark scaly 



on older trunks; leaves glabrous or sparingly pubescent or in 

 the subspecies tomentose below, acuminate even when they 

 first unfold. Fruit ripening from August to October or in the 

 South in July, stone oval P. americana. 



6. Tree not sprouting from the roots and not forming thickets, bark 



somewhat furrowed on older trunks; leaves usually strongly 

 tomentose below, commonly somewhat obtuse when they first 

 unfold. Fruit ripening in October and November, rarely 

 in September, stone obovoid to nearly round P. mexicana. 



7. Leaves orbicular to oval or rarely ovate, mostly obtuse at the 



apex, the margins incisely serrate, sometimes doubly so. 



Flowers 15 to 18 mm. broad P. subcordata. 



7. Leaves ovate, ovate-lanceolate to oval, mostly acute at the apex, 



the margins crenate or crenulate, or at least not incisely ser- 

 rate. Flowers 8 to 15 mm. broad 8. 



8. Leaves rather thick, ovate or ovate-lanceolate, only slightly lus- 



trous on the upper surface, veins usually conspicuous below, 

 the margin rather coarsely and irregularly serrate 9. 



8. Leaves usually rather thin, oblong-lanceolate to oval, lustrous 



on the upper surface, veins not very conspicuous, the margin 

 finely and evenly serrate 12. 



9. Tree not sprouting from the roota and not forming thickets; 



leaves 7.5 to J 1 cm. long. Flovjers 12 to 15 mm. broad P. hortulana. 



9. Shrubs sprouting from the rool/i and forming thickete; leaves 



mostly 5 to 7.5 cm. long. Flovjcrs 'J to 10 mm. broad 10. 



