=Remarks.=--This is the most abundant birch of Indiana. In fact all
other species are too rare to be of economic importance. The fact that
other species of birch are so rare in Indiana, is the reason that this
species is simply called "Birch." Outside of Indiana it is known as red
birch and river birch. The principal use of this wood in this State is
for heading.
All of the birches, especially the horticultural forms, are used more or
less for ornamental planting. They are beautiful trees but are short
lived.
=4. ÁLNUS.= The Alders.
Trees or shrubs; bark astringent; staminate and pistillate catkins begin
to develop early in summer and flower the following year early in the
spring before the leaves appear; bracts of the fertile catkins thick and
woody, obdeltoid with 3-rounded lobes at the apex; nuts obovate,
reddish-brown.
Leaves sharply double-serrate, the ends of the primary
veins forming the apex of the larger teeth, glaucous
beneath; nuts with a narrow thick margin 1 A. incana.
Leaves single-serrate, pale beneath; nuts without margins 2 A. rugosa.
=1.= =Alnus incàna= (Linnæus) Muenchhausen. Speckled Alder. Plate 36.
Shrubs or small trees; bark generally smooth and a reddish-brown with a
tinge of gray, with grayish dots, hence its name; twigs hairy at first,
becoming smooth by the end of the season and a golden or reddish-brown
with many fine dark specks; leaves broadly-oval, acute or short-pointed
at apex, usually broadly rounded at the base, average blades 6.5-11 cm.
long, glaucous beneath, hairy on both sides on unfolding, at maturity
becoming glabrous above or with a few hairs on the veins, beneath
remaining more or less hairy until late in autumn when usually only the
veins are hairy; pistillate catkins resembling small cones, 1-1.5 cm.
long and usually 7-12 mm. wide, near the ends of the branches, usually
in clusters of 2-7.
[Illustration: Plate 36.