Shrub low, slender, attaining a height of four feet; main trunk much branched, with dark, rough bark; branches ascending, slender, leafless, unarmed; branchlets of the season puberulent. Leaves oval-orbicular, orbicular or slightly obovate, rounded, retuse or apiculated at the apex, base truncate or at least obtuse, margins sharply serrate or crenate-serrate; upper surface sparingly pubescent or glabrous, lower surface pubescent, especially on the veins.
Flowers white, one-half inch broad; borne in two or three-flowered, lateral umbels, appearing with the leaves; calyx-tube campanulate, pubescent; petals sub-orbicular, abruptly narrowed at the base; pedicels stout, stiff, pubescent.
Fruit maturing in September; globose, one-half inch in diameter, nearly black, with a light bloom, acid and astringent; stone broadly oval, rounded at the apex, acute at the base.
Prunus gravesii is now known only in Connecticut, where it is found on a gravelly ridge at Groton near Long Island Sound. It grows in the neighborhood of Prunus maritima to which it is evidently closely related. Small in describing the species gives the following differences between the Gravesii and the Maritima plums: (1) Prunus gravesii is more slender and delicate in habit, and matures its leaves and fruit earlier in the season. (2) The leaf of Prunus gravesii is small and sub-orbicular while that of the other is larger and more elongated. (3) The new species has smaller flowers with sub-orbicular petals while those of Prunus maritima are broadly obovate and gradually narrowed at the base. (4) The fruit of Prunus gravesii is smaller and more globose and has shorter pedicels. (5) The stone is more turgid and is pointed only at the base; that of Prunus maritima is usually pointed at both ends. (6) Sprouts arising from the ground do not produce flowers as they frequently do in the case of Prunus maritima.
The cultivation of this plum has not been attempted and as compared with Maritima it promises little for the fruit-grower.
22. PRUNUS ORTHOSEPALA Koehne
1. Koehne Deut. Dend. 311. 1893. 2. Sargent Gar. and For. 7:184, 187 fig. 1894. 3. Bailey Cyc. Am. Hort. 1450. 1901.
Shrub four or five feet high; branches dense and twiggy; stems sometimes armed with slender spines; bark separating in large, loose scales; branchlets stout, slightly zigzag, reddish-brown becoming dark brown.
Winter-buds obtuse, three-lobed at maturity; leaves oblong-ovate, thin and firm, acuminate, long-pointed, two and one-half to three inches long, two-thirds inch broad, unequally cuneate or rounded at the base; margins closely serrate with incurved, calloused or rarely glandular teeth; upper surface glabrous, light green, lower surface paler and pilose; petioles slender, slightly grooved, puberulous, one-half inch long; glands two, large, at the apex of the petiole.
Flowers appearing after the leaves; borne in three or four-flowered fascicles on stout pedicels one-half inch long; calyx-tube turbinate; lobes puberulous on the outer surface, with thick tomentum, often tipped with red on the inner surface; petals narrowly obovate, rounded at the apex, narrowing at the base into slender claws, white or tinged with pink; stamens orange, exserted; style glabrous, thickened at the apex into a truncate stigma.