SUMMER KEY TO THE SPECIES OF ULMUS 
a. Leaves essentially smooth on both sides; branches often 
with corky, wing-like ridges; lowermost branches usually 
short and strongly drooping; main trunk usually continuous 
into the crown without dividing, giving to the tree a nar- 
row-oblong outline. ......... ec cee cee eee U. racemosa, p. 129. 
aa. Leaves usually rough on one or on both sides; branches 
without corky ridges; lowermost branches not short, not 
strongly drooping; main trunk usually dividing into several 
large limbs, giving to the tree a more or less vase-shaped 
outline. 
b. Leaves usually rough above, but smooth beneath, with 
petioles glabrous; bark of trunk gray, deeply fissured into 
broad, scaly ridges; inner bark ‘not mucilaginous........ 
assay stone ear eae aa Nein oe U. americana, p. 127. 
bb. Leaves usually rough both sides, with petioles hairy; bark 
of trunk dark red-brown, shallowly fissured into large, 
loose plates; inner bark mucilaginous..... U. fulva, p. 125. 
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