18 



BULLETIN 179^ U. S. DEPAKTMENT OF AGPJCULTUEE. 



tion, the Academy of Natural Sciences of Philadelphia, the Milwaukee 

 Pubhc Museum, the University of Wisconsin, the University of Min- 

 nesota, the Kansas Agricultural College, the Michigan Agricultural 

 College, the Northwestern University, the Chicago Academy of 

 Sciences, the Leland Stanford Jr. University, the University of 

 CaHfornia, and the Field Museum. 



SYNOPSIS OF THE SPECIES. 



Americana group: 

 Prunus nigra. 

 americana. 

 mexicana. 

 Subcordata group: 



Prunus subcordata. 



subcordata oregana. 

 Hortulana group : 



Prunus hortulana. 

 hortulana mineri. 

 reverchonii. 

 rivularis. 

 Angustifolia group: 



Prunus munsoniana. 

 orthosepala. 

 angustifolia. 

 angustifolia watsoni. 

 angustifolia varians. 

 Maritima group: 



Prunus alleghaniensis. 

 alleghaniensis daAdsii. 



PLUMS — continued . 



Maritima group — Continued. 

 Prunus umbellata. 



umbellata injucunda. 

 umbellata tarda, 

 grave sii. 

 maritinia. 

 Gracilis group: 



Prunus gracilis, 

 venulosa. 



CHERRIES. 



Prunus pennsylvanica. 



pennsylvanica corymbulosa. 



emarginata. 



emarginata villosa. 



DWARF CHERRIES. 



Prunus pumila. 

 cuneata. 

 besseyi. 



KEY TO THE S^ECIES.i 



1. Leaves various m 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 tvith 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. Flowers in umbelliJce clusters, the calyx lobes 

 small, obtuse, and glabrous 19. 



2. Leaves usually with at least the petiole finely pubescent along 



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 3. 



2. Leaves glabrous even to the petiole, or pubescent in some 

 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 18. 



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. 



