52 BULLETIN 179, U. S. DEPARTMENT OF AGRICULTURE. 
Type specimens in the economic collection of the United States 
Department of Agriculture were collected, flowers, May, 1910, by 
O. F. Barnes, about 10 miles northeast of Roscommon, foliage and 
fruit September 23, 1910, by W. F. Wight, No. 4698, about 4 miles 
south of Houghton Lake, Mich. Attention was first called to this — 
plum by C. A. Davis, of the United States Geological Survey, who . 
had observed a blue-fruited plum of the maritima type-growing along 
the gravelly ridges in the region south of Houghton Lake. Mr. 
Davis believed it would be found to be an undescribed species, and 
it is accordingly named for him. It differs from the species mainly 
in its leaves, which are broader in proportion to their length and less 
acuminate toward the apex. It may be distinguished from Prunus 
marituma by the reddish color of the young twigs, the more glabrous 
leaves, glabrous pedicels, and by the stone being pointed instead of 
rounded at the base. 
The fruit is used locally in making jellies and conserves. 
Prunus UmpBezata Elliott. 
(Sloe.) 
Prunus umbellata Elliott, 1816, Sketch Bot. 8. C. and Ga., v. 1, p. 541. 
Leaves lanceolate, oblong-lanceolate or oval (Pl. V, fig. 4), 4 to 7 
cm. long, 1.2 to 3 cm. broad, in age becoming rather firm in texture, 
narrowed or rarely rounded at the base, usually acute at the apex, 
the margin finely serrate with acute, incurved, rarely gland-tipped 
teeth, glabrous above, usually pubescent below along the midrib, 
and sometimes also along the lateral veins and the margin of the 
blade toward the base, marked with one or two glands near the base 
of the blade or toward the apex of the petiole, or eglandular; petioles 
mostly 5 to 7 mm. long, pubescent, at least along the upper surface. 
Flowers 10 to 18 mm. broad, appearing before the leaves the last of 
February or in March, in umbels of 2 to 4; pedicels 8 to 10 mm. long, 
slender and glabrous; calyx tube narrowly obconic, glabrous, about 
3 mm. long, the ovate, obtuse lobes 1.5 to 2 mm. long, very obscurely 
hairy without, more strongly pubescent within, entire or minutely 
toothed at the apex, mainly erect at anthesis; petals oblong-cbovate 
to nearly orbicular, 4 to 6 mm. long. Fruit globose, about 12 to 20 
mm. in diameter, red, yellow, or more often dark purple when fully 
ripe, and covered with a glaucous bloom, ripening from the last of 
July to September; stone oval or nearly globose (PI. XII, figs. 7 to 13), 
about 11.5 to 15 mm. long, 8.5 to 11 mm. broad, 6.5 to 8 mm. thick, 
obtuse or sometimes slightly pointed at the ends, variously grooved 
near the ventral and usually along the dorsal edge, the surface smooth 
or reticulate. } : 
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