18 BULLETIN 179, U. S. DEPARTMENT OF AGRICULTURE. 
tion, the Academy of Natural Sciences of Philadelphia, the Milwaukee _ 
Public Museum, the University of Wisconsin, the University of Min- | 
nesota, the Kansas Agricuitural College, the Michigan Agricultural | 
College, the Northwestern University, the Chicago Academy of 
Sciences, the Leland Stanford Jr. University, ae University off 
California, and the Field Museum. | 
SYNOPSIS OF THE SPECIES. 
PLUMS. 
Americana group: 
Prunus nigra. 
americana. 
mexicana. 
Subcordata group: 
Prunus subcordata. 
subcordata oregana. 
Hortulana group: 
Prunus hortulana. 
hortulana mineri. 
reverchonil. 
rivularis. 
Angustifolia group: 
Prunus munsoniana. 
orthosepala. 
angustifolia. 
angustifolia watsoni. 
angustifolia varians,. 
Maritima group: 
Prunus alleghaniensis. 
alleghaniensis davisii. 
PLuMsS—continued. 
Maritima group—Continued. 
Prunus umbellata. 
umbellata injucunda. 
umbellata tarda. 
eravesil. 
maritima. 
Gracilis group: 
Prunus gracilis. 
venulosa.. 
CHERRIES. 
Prunus pennsylvanica. 
pennsylvanica corymbulosa. 
emarginata. 
emarginata villosa. 
| DWARF CHERRIES. 
| Prunus pumila. 
cuneata. 
besseyl. 
KEY TO THE SPECIES.! 
1. Leaves various in form, the serrations extending practically to 
the base, somewhat pale below or green on both surfaces. 
Flowers with the calyx more or less pubescent, except in Prunus 
nigra (northern species with large flowers and reddish calyx) and 
in species with more or less corymbose inflorescence ...---...--- 2. 
1. Leaves obovate-spatulate or sometimes lance-oval on succulent 
shoots, entire toward the base and pale below with a glau- 
couslike color. lowers in umbellike clusters, the calyx lobes 
small, obtuse, and glabrous 
Leaves usually with at least the petiole finely pubescent along 
bo 
the upper edge or a few scattered hairs along the midrib below 
or with small tufts in the axils of the lateral veins. Inflores- 
cence umbellike; fruit 12 to 35 mm. in diameter, usually 
with more or less bloom, flesh edible 
Leaves glabrous even to the petiole, or pubescent in some 
bo 
forms, but not more so along the midrib than elsewhere and 
not tufted in the axils. 
Inflorescence more or less corymbose; 
fruit 6 to 10 mm. in diameter, without any trace of bloom, 
flesh thin and sour-..--.--..--- 
1 Since flowers appear before mature foliage, that part of the key referring to the inflorescence has been 
italicised to facilitate its use with the character of material to be identified. 
