216 



AMYGDALACEAE. THE PLUM FAMILY. 



Trees or shrubs with alternate, simple, petioled and usually serrate 

 leaves; flowers perfect, calyx and corolla 5 numerous, stamens 15-30; 

 fruit a 1 -seeded drupe. 



The characters which separate the species are not at all constant, 

 and the species often vary much in the extremes of their range. 



PRUNUS. THE PLUMS AND CHERRIES. 



Flowers in umbel like clusters, or somewhat corymbose, ap- 

 pearing before or with the leaves on branchlets of the 

 preceding year. 

 Margins of leaves with sharp teeth. 



Petioles glabrous beneath 1 P. americana. 



Petioles more or less pubescent all around 2 P. americana 



var. lanata. 

 Margins of leaves with blunt or crenate teeth. 



Teeth of center of leaves about 10 per cm. ; calyx lobes 



glandular; fruit more than 10 mm. in diameter. 

 Principal leaves of fruiting branches generally more 

 than 4 cm. broad; flowers white and generally more 



than 17 mm. wide 3 P. nigra. 



Principal leaves of fruiting branches generally less than 

 4 cm. broad; flowers white which on age show a 

 tinge of pink and generally less than 17 mm. wide. 4 P. hortulana. 

 Teeth of center of leaves about 20 per cm.; calyx lobes 



glandless; fruit less than 10 mm. in diameter 5 P. pennsylvanica. 



Flowers in racemes, appearing after the leaves on twigs of 



the present year 6 P. serotina. 



1. Primus americana Marshall. WILD RED PLUM. Plate 99 

 Small trees with crooked branches; bark of old trees exfoliating in 

 irregular plates; twigs smooth; leaves obovate or oval, 5-9 cm. long, 

 2.5-5 cm. wide, narrowed or sometimes rounded at the base, acuminate 

 at apex, margins sharply serrate or doubly serrate, glabrous above and 

 smooth below, or hairy on the veins and sometimes more or less pube- 

 scent over the whole under surface, inner surface of petiole more or less 

 hairy and sometimes bearing one or two glands; flowers appear in April 

 or May before or with the leaves in clusters of 2-4 or sometimes singly, 

 about 2 cm. in diameter, calyx smooth or with some hairs near the base 

 of the lobes which are pubescent within and smooth or hairy without, 

 lobes entire or cut-toothed above the middle, glandless or with incon- 

 spicuous glands; fruit ripens in August or September, usually globose, 

 about 2 cm. in diameter, red; stone doubly convex, oval to nearly 

 orbicular, surface usually smooth. 



