and Old World Birches. 175 
a Niagara specimen collected by Asa Gray; and Piper’s No. 
1,128 from Whatcom Co., Washington, cannot be distinguished 
from Lowrie’s material from Bald Eagle Mt., Blair Co., Penn- 
sylvania (sheet No. 149,835, U.S. Nat. Herb.), and the old 
specimen of Wm. Oakes’s from Topstield, Massachusetts, re- 
ferred by Regel to 2B. occidentalis, var. commutata ; and in 
their leaves these trees very closely approach a Canoe Birch 
growing at Oak Island, Revere, Massachusetts, and well-known 
to the local botanists from its lustrous brown bark. From 
herbarium specimens, then, there is no character by which to 
separate the northwestern Betula occidentalis from the eastern 
B. alba ( papyrifera). 
he important character upon which Professor Sargent lays 
stress in his recent note* is the color of the bark, which in the 
_ horthwestern tree is usually brown. This character alone seems 
hardly sufficient to separate specifically the two trees, espec- 
ially in view of such brown-barked trees in the East as that on 
Oak Island; a tree growing at the foot of Mountain Rock, 
Ellsworth, Maine (represented in the Gray Herbarium), with 
gray-brown bark strongly tinged with plum-color; and Robin- 
son and Schrenk’s No. 139, from Newfoundland, in which the 
old bark, though becoming pale, retains much of the brown 
which is often seen in young trees. Furthermore, it is worthy 
of note that the Pacitic Coast tree is not thoroughly constant 
in its bark. The Henderson plant of 1888, from the Gulf of 
Georgia (essentially the type locality), was sent to the late 
Sereno Watson, who called it B. occidentalis. Subsequently, 
however, Professor Henderson, writing under date of Decem- 
ber 9, 1897, of the difficulties in studying this group, said: 
“Just where B. papyrifera leaves off and B. occidentalis be- 
gins, I am, and always have been, at a loss to say.” He then 
comments upon a tree which “is undoubtedly B. papyrifera 
In every respect,’ adding, ‘and I have no doubt that my num- 
ber 1,712, from the shores of Lummi Island, Gulf of Georgia, 
sent Mr. Watson in ’88, and referred by him to B. occidentalis, 
Is the same thing.” Thus it would seem that Betula alba 
(papyrifera) is not constant in its pale bark in the East, and 
that B. occidentalis of the Northwest may not always be dis- 
tinguished by its dark bark. 
The tendency of another dark-barked northwestern tree to 
become quite as pale as the eastern Canoe Birch will be noted 
in the discussion of a species soon to be considered ; but in this 
connection it is worth while to note a tendency to darkening 
of color which has been observed in certain other northwestern 
plants, It is well known that many species of Carea growing 
in shade or in southern areas have pale or hyaline scales, while 
* Bot. Gaz., I. c. 
