and Old World Birches. 171 
Betula alba (as interpreted by Roth). 
As already stated, Betula alba, L. (as interpreted by Roth) 
has passed in Europe as B. pubescens, and under this latter 
name it is ordinarily distinguished from 2B. pendula, Roth 
(B. verrucosa, Ehrh.). The species is generally recognized as 
occurring through northern and central Europe and across 
Asia, and by Regel and his followers it was regarded as like- 
wise American, though by recent authors it has been excluded 
from our flora. The typical form of £B. alba is the large 
White Birch of northern Europe, with ascending branchlets, 
puberulent or hairy twigs, and ovate or rhombic-ovate leaves 
more or less pubescent beneath, especially when young. 
he representative of this tree in America is our common 
Paper or Canoe Birch, Betula papyrifera, Marsh.* (B. papy- 
racea, Ait.+), which was discussed in detail by Michaux in his 
Sylva.t There Michaux wrote at such length as “ will not be 
deemed superfluous by persons who justly appreciate the im- 
portance of precise ideas on subjects like the present,” of the 
Canoe Birch (B. papyracea), the European White Birch (B. 
alba, including, at least in the illustration, B. pendula, Roth), 
and the American White or Old Field Birch (B. populifolia). 
Michaux’s plate of Betula papyracea is of a northern form 
very closely approaching var, cordifolia, Regel; and in com- 
menting upon this tree he said “the bark is of a brilliant 
white, like that of the White Birch of Sweden, and, like that 
too, it is almost indestructible... ... is bark, like that of 
the European species, is devoted to many uses,” which are 
very fully enumerated. In his discussion of the European 
. alba he said, “The trunk and limbs of the large trees are 
covered with a thick bark, whose epidermis is white and _per- 
fectly similar to that of the White Birch [B. populifolia] and 
the Canoe Birch [B. papyracea|. The small branches like- 
wise resemble those of the species just mentioned [B. papy- 
racea|, being slender, flexible, and of a brown color spotted 
with white.” He then discussed the uses of the European 
White Birch, concluding his remarks with: “Such are the 
principal uses of the European Birch, all the valuable proper- 
ties of which are completely united in the Canoe Birch of 
orth America.” In his discussion of B. populifolia, Michaux 
further said: “The trunk of this species is clad in a bark of 
as pure white as that of the Canoe Birch and of the European 
Bireh ; but its epidermis, when separated from the cellular 
tissue, is incapable of being divided, like that of the two pre- 
ceding species, into thin sheets; which constitutes an essential 
* Arbust. Am., 19 (1785). + Hort. Kew, iii, 337 (1789). 
t Michaux, Sylva, ii, 50-57. 
