72 THE PLUMS OF NEW YORK. 



being one of the most constant differences. (4) The flowers of Nigra appear 

 several days earlier, are larger and are more pink than those of Americana. 

 (5) The calyx-lobes of Nigra are glandular and the leaf -stalks are bi -glandu- 

 lar, characters usually not found in Americana. The calyx in all its parts 

 is glabrous or at least far less pubescent than in Americana and if present 

 the hairs are short and stiff, whereas in Americana the pubescence is 

 soft. (6) The fruit of Nigra ripens earlier and is darker in color with less 

 bloom and is more oblong than that of Americana. The skin of the plum 

 is thinner and is not so objectionable either cooked or eaten out of hand. 

 (7) The stone of Nigra is usually larger, flatter and more strongly crested. 

 The characters of the two species vary much in different individuals and 

 there are many intermediate forms but the differences seem as constant as 

 between other species of this variable genus. 



The Nigra plums are important horticulturally because they can be 

 grown in somewhat colder regions than the Americanas. They not only 

 endure more cold than the last named group, but their toUgh wood enables 

 them to stand better the weight of snows and the stress of winds. Their 

 earliness, too, prolongs the season for this type of fruit and in regions 

 where the season is short they may be grown with more certainty than other 

 groups. In habits and characters other than those named they are so 

 like the Americana as to need no further discussion. About forty varieties 

 of this species are under cultivation. 



13. PRUNUS ALLEGHAWIENSIS Porter 



1. Porter So/. Gaz. 2:85. 1877. 2. Ibid. Gar. and For. 3:428, fig. 53. 1890. 3. Sargent Sil. 

 N. Am. 4:27, PI. 153. 1892. 4. Bailey Ev. Nat. Fr. 225. 1898. 



Tree low, slender, straggling, fifteen to eighteen feet in height, or a low shrub; 

 trunk-diameter from five to eight inches; bark dark brown, surface fissured and scaly; 

 branches numerous, upright, rigid, seldom spiny; branchlets pubescent, becoming 

 glabrous and red, turning to dark brown; lenticels many, small, white. 



Leaves ovate-oblong or lanceolate, sometimes obovate, apex acute or acuminate, 

 base rounded, margin sharply serrate, teeth fine and tipped with glands, in texture thick 

 and firm; upper surface dark green and glabrous; lower surface light green, glabrous 

 except on the veins and midrib; petioles short, slender, pubescent; glands two, large, 

 at the base of the blade. 



Flowers white, fading to pink, one-half inch across, appearing with the leaves; 

 borne in two to five-flowered umbels; pedicels slender, finely tomentose, from one- 

 fourth to one-half inch in length; calyx-tube narrowly obconic; calyx-lobes entire, 

 pubescent on the outer, tomentose on the inner surface; petals rounded but narrowing 



