ROSACES 511 



Calyx-lobes acute, with laciniate margins ; stone depressed-globose ; leaves entire. 



16. P. sphaerocarpa (D). 

 Calyx-lobes acute, entire ; stone ovate, slightly compressed. 



Leaves coarsely spinulose-toothed. 17. P. ilicifolia (G). 



Leaves entire or occasionally remotely and minutely dentate. 



18. P. integrifolia (G). 



1. Flowers in axillary umbels; fruit usually more than \' in diameter. PLUMS. 



1. Primus nigra, Ait. Red Plum. Canada Plum. 



Leaves oblong-ovate to obovate, abruptly contracted at the apex into long narrow 

 points, wedge-shaped, truncate or slightly heart-shaped at the base, and doubly 

 crenulate-serrate, with small dark glandular teeth, when they unfold faintly tinged 

 with red and pubescent on the under surface or glabrous with the exception of con- 

 spicuous tufts of slender white or rufous hairs in the axils of the primary veins, and 



at maturity thick and firm, dull dark green on the upper, pale on the lower surface, 

 3'-5' long and l^'-3' wide, with conspicuous pale midribs and slender veins; their peti- 

 oles stout, '-!' long, and biglandular at the apex, with 2 large dark glands; stipules 

 lanceolate or on vigorous shoots often 3-5-lobed, glandular-serrate, ' long, early 

 deciduous. Flowers appearing in early spring with or before the leaves, \' in diam- 

 eter, on slender glabrous dark red pedicels, '-' long, in 3 or 4-flowered umbels; 

 calyx-tube broadly obconic, dark red on the outer, bright red on the inner surface, 

 the lobes narrow, acute, glandular, glabrous or occasionally pubescent on the outer 

 surface, reflexed after the flowers open; petals broadly ovate, rounded at the apex, 

 more or less erose on the margins, contracted at the base into short claws, white, 

 turning pink in fading. Fruit ripening from the middle to the end of August, oblong-* 

 oval, I'-l^' long, with a tough thick orange-red skin nearly destitute of bloom, yellow 

 rather austere flesh, and an oval compressed stone, 1' long, ' wide, thick-walled, 

 acutely ridged on the ventral and slightly grooved on the dorsal suture. 



A tree, 20-30 high, with a trunk sometimes 5'-6' in diameter, divided usually 

 5-6 from the ground into a number of stout upright branches forming a narrow 

 rigid head, stout slightly zigzag branchlets marked by numerous pale excrescences, 



