and Old World Birches. 488 
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 Miquel* as a variety of the 
Eurasian Betula alba ; while by Rehder it is more properly con- 
sidered a variety of the subspecies B. pendula (L. verrucosa). 
This disposition of the tree seems most advisable, since typical 
B. pendula crosses northern Asia and is distinguished from 
the trees which Siebold called B. japonica 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. alaskana, should be 
known, then, as Betula pendula, Roth, var. japonica (Siebold), 
Rehder in Bailey Cye. Am. Hort. i, 159. 
Reference has been made to the tendency of Betula alba 
a character to be confidently relied upon. Furthermore, Mr. 
Coville writes of 8B. kenaica under date 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 dithcult 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 National Herbarium 
show strips of lichen-covered bark of B. kenaica no darker 
* Miquel, Ann, Bot. Mus. Lugd. Bat. ii, 136. 
te ee in letter to Sir Wm. Hooker, Palliser, Rep. Brit. N. A. Expl. 
¢ Bourgeau, 1. c. 249; see also Hooker, ibid., 260; Gray, ibid., 263; Sulli- 
van, ibid., 85, ete. 
Am. Jour, Sc ne Serres, Vou, XIV, No. 81.—SepremsBer, 1902, 
