BETULACEAE. 23 
BETULA. Birch. 
(Family Betulaceae). 
Trees or less commonly shrubs: 
deciduous. Twigs slender, usu- 
ally zig-zag, terete, frequently de- 
veloping as dwarf-shoots so as 
to make the lateral buds appear 
stalked: pith minute, compressed 
3-sided, continuous, green. Buds 
moderate, solitary, fusiform ovoid, 
sessile, with 2 or 3 exposed scales, 
the end-bud usually deciduous ex- 
cept on the numerous short spurs. 
Leaf-scars alternate, more or less 
2-ranked, half-elliptical, small: ° 
bundle-traces 3, sometimes indis- 
tinct: stipule-scars narrow. 
Though they have been much 
confused in botanical publications, 
the birches are not very difficult 
as a rule. In accordance with the 
policy of adhering to the nomen- 
clature of the Standard Cyclope- 
dia of Horticulture, the names here used are somewhat differ- 
ent from those employed in the last edition of Gray’s Manual, 
though the latter rest on an extended critical study of the 
group by Fernald, published in full in The American Journal 
of Science for September, 1902. 
An excellent character is derived from the brace of the 
fruiting cones, which are sometimes available in winter; and 
this character has been applied successfully to the recognition 
of certain hybrid birches by Rosendahl in volume four of 
Minnesota Botanical Studies. 
