STANDEE Y TUBES AND SHRUBS OF MEXICO. 339 



Leaves serrate or serrulate. 



Leaf blades or))iciilar or broadly ovate, finely serrate; flowers pedi- 

 cellate 5. P. fremontii. 



Leaf blades oblong or obovate, serrate ; flowers subsesslle. 



6. P, microphylla. 

 Flowers racemose ; ovary glabrous. 

 Racemes terminating short leafy branches ; leaves finely serrulate. 

 Leaf blades mostly 4 to G cm. long, obtuse or acute ; racemes 4 to 6 



cm. long 7. P. virens. 



Leaf blades mostly 6.5 to 10 cm. long, abruptly acuminate or long- 

 acuminate; racemes usually 7 to 15 cm. long 8. P. capuli. 



Itacemes axillary, naked ; leaves entire or coarsely serrate or dentate. 

 Leaves serrate or dentate, or rarely entire, the fruit then 1.5 to 2 cm. 

 long. 



Leaves entire 9. P. lyoni. 



Leaves serrate or dentate. 

 Leaf blades suborbicular or rounded-ovate ; racemes equaling or longer 



than the leaves 10. P, ilicifolia. 



Leaf blades lance-oblong; racemes much shorter than the leaves. 



11. P. prionophylla. 

 Leaves entire. 



Calyx persistent beneath the fruit. Leaves barbate beneath. 



12. P. rhamnoides. 

 Calyx deciduous. 



Calyx villous within at the base; petals barbate above the base. 



13. P. corta,pico. 

 Calyx glabrous within ; petals glabrous. 



Racemes all or mostly in clusters of 2 to 4 14. P. samydoides. 



Racemes solitary. 



Leaf blades without glands beneath; branches tiiher<nil;ite by the 



elevated lenticels 15. P. tuberculata. 



Leaf blades with 2 or more glands beneath near the base; 

 branches smooth or nearly so. 

 Glands 3 or 4 beneath. 2 of them near the base close to the 



costa, the others near the lateral veins 16. ?. tetradenia. 



Glands 2, at the base of the blade near the costa. 



Petioles 5 to 10 mm. long; petals 2.3 to 2.7 mm. long; anthers 

 1 to 1.2 mm. long; stigma 1.3 to 1.5 mm. broad. 



17. P. erythroxylon. 

 Petioles 12 to 22 mm. long: petals 1.5 to 2 mm. long; anthers 

 0.6 to 0.8 mm. long; stigma 0.4 to 1 mm. broad. 



.18. P. brachybotrya. 

 1. Prunus niexicana S. Wats. rroc. Anier. Acad. 17: 353. 18S2. 



Coahuila and Nuevo Leon ; type from Lerios, Coahuila. Southern United 

 States. 



Small tree; leaves lanceolate or ovate, 5 to 12 cm. long; flowers white. 2 cm. 

 broad ; fruit purplish red, with a bluish bloom, sometimes 2.5 cm. in diameter. 



This species has often been confused with P. amcricana IMarsh. and P. nigra 

 Ait., both natives of the United States. Those two species are the source of 

 many of the cultivated plums. In the wild state the fruit is of fair quality, but 

 it is greatly improved by cultivation. There is reason to believe that these 

 wild plums were cultivated by the Indians, although, as Havard remarks, the 

 Indian orchards were perhaps only the result of seeds accidentally dropped 

 about villages and camping grounds. 



