dd. Lower sides of leaves paler than the upper;

leaflet-margins entire or obscurely serrate. _F. americana_, p. 213.

WINTER KEY TO THE SPECIES OF FRAXINUS

a. Twigs prominently 4-angled; fruit falling in early autumn. _F. quadrangulata_, p. 219.

aa. Twigs terete; fruit often persistent on the tree until mid-winter or the following spring.

b. Buds rusty-tomentose; twigs more or less downy. _F. pennsylvanica_, p. 215.

bb. Buds not tomentose; twigs not downy.