WINTER KEY TO THE SPECIES OF PRUNUS 
a. Terminal bud present; bark of young trunks rather smooth. 
b. Buds clustered at the tips of ali shoots; twigs usually less 
than 14¢ inch thick; pith of twigs brown................ 
SOs Re eeenaAas pea aaads P. pennsylvanica, p. 159. 
‘bb. Buds not clustered, or clustered only on short, spur-like 
branchlets; twigs usually more than 4, inch thick; pith 
of twigs white. 
c. Buds usually %4 inch or less in length; bud-scales uni- 
form in color, apiculate at the apex; bark on old trunks 
blackish, rough-scaly ;*small to large tree.............05 
breccia egy Se MAGE eee eLY abs P. serotina, p. 155. 
ce. Buds usually 14-14 inch long; bud-scales grayish on the 
margins, rounded at the apex; bark on old trunks brown, 
smooth or only slightly fissured; usually a large shrub 
erties waaie alee auatiare ean Apetatis hemes P. virginiana, p. 157. 
aa. Terminal bud absent; bark of young trunks early splitting 
off in large, thick plates............00eee ees P. nigra, p. 161. 
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