SUMMER KEY TO THE SPECIES OF 

 FRAXINUS 



a. Lateral leaflets sessile F. nigra, p. 221. 



aa. Lateral leaflets petioled. 



t>. Twigs, petioles and lower sides of leaves pubescent 



F. pennsylvanica, p. 215. 



bb. Twigs, petioles and lower sides of leaves essentially glab- 

 rous. 



c. Twigs prominently 4-angled F. quadrangulata, p. 219. 



cc. Twigs terete. 



d. Lower sides of leaves essentially of the same color 

 as the upper; leaflet-margins rather finely sharp- 

 serrate F. Pennsylvania lanceolata, p. 217. 



dd. Lower sides of leaves paler than the upper; leaflet- 

 margins entire or obscurely serrate 



F. americana, p. 213. 



210 



