and Old World Birches. 183 



This Asian tree, which presents indiscriminate variation in 

 the size and toothing of its leaves and the abundance of resin 

 on its branches, was treated by Miqiiel^ as a variety of the 

 Eurasian Betida cdha ; while by Rehder it is more properly con- 

 sidered a variety of the subspecies B. pendida {B. vemicosa). 

 This disposition of the tree seems most advisable, since typical 

 B. jjendida crosses northern Asia and is distinguished from 

 the trees which Siebold called B. jccponica and Regel called 

 B. latifolia only by an inconstant tendency of the leaves to 

 be more cuneate at base. The form of the tree with broad 

 leaves rounded or truncate at base, common in northern Asia, 

 and including much of B. kenaica and B. alaskoyna^ should be 

 known, then, as Betida pendida, Roth, var. japonica (Siebold), 

 Rehder in Bailey Cyc. Am. Hort. i, 159. 



Reference has been made to the tendency of Betula alba 

 to develop brown bark ^^hen it occurs upon the northwest 

 coast of America. Similar reddish or brown bark likewise 

 ordinarily distinguishes the northwestern tree which has been 

 called B. henaica (B, alaskana) from the true B. pendida. 

 But this is not a sufficiently constant character to separate it 

 specifically from the Asian specimens which so closely match 

 it in every detail shown in the herbarium. The writer has 

 been unable to find any clear statement that the bark of B. 

 pendula, var. jcqyonica^ is eitlier white or brown. Bourgeau, 

 however, who had previously remarked upon the abundance of 

 Betula jyajyyrifera on He Royale, Lake Superior,f and who 

 was consequently familiar with the ordinary white-barked 

 tree, referred the Saskatchewan tree without question to that 

 species ;:{; and Macoun referred his Prince Albert tree without 

 comment to B. jpapyrifera. The fact that these acute collec- 

 tors of the first mentioned specimens of B. alaskana saw in 

 their Saskatchewan trees only the white-barked B. jpapyrifera 

 is sufficient evidence that the brown bark of B. alaskana\^ not 

 a character to be confidently relied upon. Furthermore, Mr. 

 Coville writes of B. kenaica under elate of March 12, 1901 : 

 " In certain individual trees, however, and perhaps on exposure 

 to certain climatic conditions the layers of the bark separate 

 and the bark turns white as in papyrifera. This factor has 

 made it difficult for the collectors who have observed the tree 

 to tell whether in upper Cook's Inlet there is a white-barked 

 birch distinguishable from kenaica.''^ Sheets Nos. 373,611, 

 373,619, and 373,620 in the United States iS"ational Herbarium 

 show strips of lichen-covered bark of B. kenaica no darker 



* Miquel, Ann. Bot. Mus. Lugd. Bat. ii, 136. 



f Bourgeau in letter to Sir Wm. Hooker, Palliser, Eep. Brit. N. A. Expl. 

 Exped. 217. 



X Bourgeau, 1. c. 249 ; see also Hooker, ibid., 260 ; Gray, ibid., 263 ; Sulli- 

 van, ibid., 85, etc. 



Am. Jour. Sci. — Fourth Series, Vol. XIV, No. 81.— September, 1902. 

 13 



