AMERICAN JOURNAL OF SCIENCE 
[FOURTH SERIES.] 
Art. XX.—The Relationships of some American and Old 
World Birches; by M. L. Fernatp. (With Plates V-VL.) 
[Contributions from the Gray Herbarium of Harvard University, New 
Series, No. xxiii. ] 
A RECENT attempt satisfactorily to identify some birches 
from the alpine summits of New England has made it neces- 
sary to study in detail certain species of the Old World. In 
this detailed study so many well-known European and Asian 
forms have been found identical with trees and shrubs of 
America which have ordinarily passed as endemic, that the fol- 
lowing notes are offered as a partial solution of the difficulties 
which have long surrounded the species of Betula. The 
writer has been specially fortunate in having constant access 
i i Sccietiim which 
ada has been generously loaned by Messrs. F. V. oville and 
J. M. Macoun, the collections of the Arnold Arboretum have 
sors L. F. Henderson and C. V. Piper. Thus it has been 
possible to examine a very complete representation of the 
enus. 
The birches are trees of boreal range. Unknown in the 
southern hemisphere and the tropics, they abound throughout 
the northern and mountainous sections of North America, 
Europe and Asia, reaching a more extreme northern range on 
both continents than any other trees.t By Regel and other 
* Regel in DC. Prodr., xvi, part 2 (1864), 161-189. . 
+See F, A. Michaux, Hist. des Arb., ii, 129, and Sylva, ii, 47; Sargent, 
Silva, ix, 46; Rehder in Bailey, Cye. Am. Hort., i, 158. 
Am. Jour, 6 ilar Series, Vou. XIV, No. 81.—SEPTEMBER, 1902. 
