URTICACEAE

SUMMER KEY TO THE SPECIES OF ULMUS

a.Leaves essentially smooth on both sides; branches oftenwith corky, wing-like ridges; lowermost branches usuallyshort and strongly drooping; main trunk usually continuousinto the crown without dividing, giving to the tree a narrow-oblongoutline.U. racemosa, p. [129].
aa.Leaves usually rough on one or on both sides; brancheswithout corky ridges; lowermost branches not short, notstrongly drooping; main trunk usually dividing into severallarge limbs, giving to the tree a more or less vase-shapedoutline.
b.Leaves usually rough above, but smooth beneath, withpetioles glabrous; bark of trunk gray, deeply fissured intobroad, scaly ridges; inner bark not mucilaginous.U. americana, p. [127].
bb.Leaves usually rough both sides, with petioles hairy; barkof trunk dark red-brown, shallowly fissured into large,loose plates; inner bark mucilaginous.U. fulva, p. [125].

WINTER KEY TO THE SPECIES OF ULMUS

a.Buds conspicuously rusty-tomentose; twigs more or lesspubescent; inner bark very mucilaginous when chewed.U. fulva, p. [125].
aa.Buds not conspicuously rusty-tomentose; twigs glabrous;inner bark not mucilaginous.
b.Bundle-scars usually 3; buds 1/8 inch long, glabrous; twigswithout corky ridges; outline of tree vase-shaped.U. americana, p. [127].
bb.Bundle-scars usually 4-6 in a curved line; buds 1/4 inchlong, somewhat pilose; twigs often with corky ridges;outline of tree narrow-oblong.U. racemosa, p. [129].

Slippery Elm. Red Elm