and Old World Birches. 177 
This form (2. glutinosa,. Wallr.t) is treated by various Euro- 
pean authors as a natural hybrid between B. alba (pubescens) 
and BL. pendula,§ but the apparent absence from Maine of 
B. pendula renders this origin of the tree improbable. 
Betula alba, var. cordifolia. 
Another tree more common in the mountainous portions of 
New England than Betula alba, var. glutinosa, differs from 
the ordinary Canoe Birch only in its cordate-ovate leaves. In 
this character it is very constant, however, and seems to de- 
serve the varietal recognition given it by Regel as B. alba, 
subsp. papyrifera, B, cordifolia,| (B. cordifolia, Regel, Mon. 
28, t. 12, figs. 29-36). The species, B. cordifolia, was based 
upon one of de la Pylaie’s specimens from Newfoundland, and 
in his later treatment of the tree Regel cited two sheets in the 
ray Herbarium, one from Mt. Katahdin, Maine, the other 
from Lake Superior. The tree is common on the upper 
wooded slopes of Katahdin and other mountains of northern 
N ew England, becoming a dwarf shrub at their summits, where 
it has passed as B. papyracea, var. minor, Tuck. Tucker- 
man’s original material and description, however, was of 
another form soon to be noted. The tree or shrub of the 
mountainous districts of New England, with cordate leaves, 
pubescent on the veins beneath, may be known as Betula albu, 
var. Cordifolia (Regel). Its range is a broad one, from north- 
ern Lasrapor (CU. A. Kenaston, sheet No. 25,240, U. S. Nat. 
Herb.) and Newrounpianp to New Brunswick, Marner, the 
White Mountains, New Hampsutre, Lake Superior, Iowa 
(B. Fink, No. 109), Avnerra, Brrrisn Cotumpra, Ipauo, and 
Wasnineton. 
* Trautv. ex Regel, Mon. Bet, (1861), 20, t Regel, 1. ¢., 28. 
t Sched. Crit,, 497’ (1822), 
* See Koehne, Deutsch Dendr., 109; Guerke, 1. ¢., 48. 
| Regel in DC,, 1. c., 166. 
