and Old World Bii'ches. 171 



Betula cdha (as interpreted b}^ Roth). 



As already stated, Betida alha^ L. (as interpreted by Roth) 

 has passed in Europe as B. jjuhescens^ and under this latter 

 name it is ordinarily distinguished from B. 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. 



The representative of this tree in America is our common 

 Paper or Canoe Birch, Betida jyajpyvifera. Marsh. "^ (B. jpajpy- 

 racea^ Ait.f), which was discussed in detail by Michaux in his 

 Sylva.:}: 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. joapyracea), the European White Birch {B. 

 alha, including, at least in the ilhistration, B. pendida^ Roth), 

 and the American White or Old Field Birch {B. popidifolia). 



Michaux's plate of Betida 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 AYhite Birch of Sweden, and, like that 



too, it is almost indestructible This bark, like that of 



the European species, is devoted to many uses," which are 

 very fully enumerated. In his discussion of the European 

 B. 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. p>apyracea'\. 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 

 ]N"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 

 Birch ; 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). f Hort. Kew, iii, 337 (1789). 



X Michaux, Sylva, ii, 50-57. 



