WINTER KEY TO THE SPECIES OF PRUNUS 



a. Terminal bud present; bark of young trunks rather smooth, 

 b. Buds clustered at the tips of all shoots; twigs usually less 



than He inch thick ; pith of twigs brown 



P. pennsylvanica, p. i SO. 



bb. Buds not clustered, or clustered only on short, spur-like 

 branchlets ; twigs usually more than ^/ic inch thick ; pith 

 of twigs white. 



c. Buds usually Y$ mcn or I GSS m length ; bud-scales uni- 

 form in color, apiculate at the apex ; bark on old trunks 



blackish, rough-scaly ; small to large tree 



P. serotina, p. 155. 



cc. Buds usually l /4- l /2 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 



P. virginiana, p. 157. 



an. Terminal bud absent; bark of young trunks early splitting 

 off in large, thick plates P. nigra, p. 161. 



153 



