ULMACEAE. 39 
CELTIS. Hackberry. 
(Family Ulmaceae). 
Trees, or a few shrubs: decidu- 
ous. Twigs rounded, slender, zig- 
zag. Pith rather small, white, 
rounded, closely chambered, or ex- 
ceptionally continuous except at 
some or all of the nodes. Buds 
sessile, solitary, ovoid or deltoid, 
closely appressed, with about 4 
2-ranked scales, the end-bud lack- 
ing. lLeaf-scars alternate, crescent 
shaped or half elliptical, somewhat 
raised: bundle-traces 3, or the mid- 
dle one divided, or confluent in a 
C-shaped group: stipule-scars nar- 
row. References under Zelkova. 
1. Buds long (3-4 mm.): bark 
ridged. (1). C. occidentalis. 
Buds short (1-2 mm.). 2. 
2. Shrub. C. pumila. 
Tree, smooth except for corky 
warts. (2).C.mississippiensis. 
PLANERA. 
(Family Ulmaceae). 
Winter characters of Ulmus, from which the warty ovary 
and unwinged fruit distinguish it in early spring. Our na- 
tive species, P. aquatica, in bud and twig somewhat resem- 
bles U. pumila, but its red-brown puberulent buds are some- 
times somewhat elongated so as to resemble those of U. alata, 
from which it differs in the absence of corky wings on the 
second year’s growth. 
References to Planera in winter are given under the next 
genus, Zelkova. 
