SUMMER KEY TO THE SPECIES OF PRUNUS 



a. Leaves oblong-ovate to obovate, abruptly acuminate at the 

 apex ; marginal teeth not incurved. 



b. Margin of leaves sharp-serrate with spreading teeth; 

 leaves not rugose, the veins not prominent; fruit 1 A~ 1 A 

 inch long, bright red, racemose, July- August; bark of 

 trunk brown, smooth or only slightly fissured; usually a 



large shrub P. virginiana, p. 157. 



hi). Margin of leaves crenate-serrate ; leaves more or less 

 rugose, the veins prominent ; fruit about I inch long, 

 orange-red, clustered, August-September; bark of trunk 

 gray-brown, early splitting off in large, thick plates; 



a small tree P. nlgra, p. 161. 



aa. Leaves oval to oblong-lanceolate, taper-pointed at the apex; 

 marginal teeth incurved. 



b. Fruit light red, clustered, July- August; twigs usually less 

 than ^c inch? thick; pith of twigs brown; tree northern 



P. pennsylvanica, p. 159. 



bb. Fruit black, racemose, August-September; twigs usually 

 more than 1 /io inch thick; pith of twigs white; tree 

 southern P. serotina, p. 155. 



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