=Distribution.=--The distribution of this species is variously given as
from Newfoundland west to Manitoba and south in the Alleghenies to
Georgia. It is now definitely known that the species of _Betula_
hybridize which may account for the peculiar forms often encountered.
That there are geographic races or Mendelian segregates of this species
is evidenced by the different interpretations given this species by
different authors. _Betula alleghanensis_ Britton appears to be one of
them. The descriptive difference between _Betula lenta_ and _Betula
lutea_ is not clear, which has resulted in many authors crediting
_Betula lenta_ to Indiana and the area west of Indiana.
The preceding description does not agree with that of _Betula lutea_
exactly, and has been drawn to cover the specimens at hand from Indiana
which the author has from Allen, Crawford, Lagrange, Lake, Marshall,
Porter and Steuben Counties. It has recently been reported from White
County by Heimlich.[29] He says: "Specimens were taken from two trees
about two miles south of Buffalo near the water's edge of the river."
The writer has visited this locality and found here, and also on the
island above the bridge a little farther down the river, _Betula nigra_,
but could not find _Betula lutea_. Since Heimlich did not report _Betula
nigra_, which unmistakably occurs here, I assume he has confused the two
species. It is very local in its distribution, and appears to be
confined to swamps, borders of lakes, and streams in the extreme
northern part of the State. It has not been seen south of the northern
end of the State, except a few small trees found clinging to the walls
of the cliffs of a ravine about one mile east of Taswell in Crawford
County. The walls of this ravine are about 25 meters high; associated
with it were a few trees of hemlock, and on the top of the cliffs,
laurel (_Kalmia latifolia_).
Large trees of this species in Indiana are usually from 4-6 dm. in
diameter and about 15 m. high. The number in any one station is usually
few, although there were formerly patches where it was plentiful. Van
Gorder[30] reports for Noble County _Betula lenta_ which should be
transferred to this species, and he says: "There is a marsh of several
acres of birch in Section 15 of York Township." The largest area now
known is that contained in the large tamarack swamp near Mineral Springs
in Porter County. In this swamp are found tamarack and white cedar. It
was in this swamp that the writer found a peculiar form of birch which
has been determined as _Betula Sandbergi_. Since this species[31] is
recognized as a hybrid of _Betula papyrifera_ and _Betula pumila_
variety _glandulifera_, and the last parent of this hybrid is not found
in the vicinity, a discussion of this form is not presented. In the
immediate vicinity are found only _Betula lutea_ and _Betula pumila_.
_Betula papyrifera_ is found about a mile distant to the south. It is
assumed that this form is a cross between _Betula lutea_ and _Betula
pumila_.
=2.= =Betula populifòlia= Marshall. Gray or White Birch. Plate 33. A
small tree; bark a chalky-white, not separating into thin layers, inner
bark orange, on the trunks of old trees nearly black; shoots at first
covered with numerous glands, becoming smooth and yellowish or
reddish-brown; leaves generally long-deltoid, average blades 3-6 cm.
long, usually long taper-pointed, truncate or nearly so at the base,
irregularly double-serrate, slightly pubescent on the veins when young,
soon becoming glabrous; fertile catkins 1.5-3 cm. long and about 7 mm.
in diameter; bracts of eastern trees differ from those of Indiana trees
which are about 3-4 mm. long, lobed to about 1/3 of the distance from
the apex, lateral lobes the largest and strongly divaricate, puberulent
on the back; seed strongly notched at the apex; nut slightly obovoid;
wings much broader than the nut.
=Distribution.=--Nova Scotia west to southern Ontario and south to
Delaware and Pennsylvania. In Indiana it has been reported from Lake,
Laporte, Porter, St. Joseph and Tippecanoe Counties. There may be some
doubt about the Tippecanoe record, since many of the older records were
made from cultivated trees. The numbers of the species in Indiana were
always limited. It is not able to meet changed conditions and it has
already almost disappeared from our area. I was told that formerly this
species was found all about a lake in Laporte County, but it has all
died out. Its appearance in Indiana is peculiar since it is not found
west of us, or north in Michigan or east in Ohio. This small group of
trees near Lake Michigan is three or four hundred miles from the nearest
of their kind.
=Remarks.=--This species is called white and gray birch. The largest
tree seen in Indiana was about 2 dm. in diameter and 13 m. high.
[Illustration: Plate 33.