168 Fernald— Relationships of some American 
into account such well-known species as Carex rip 
Pseudo- Cyperus, Juneus tenuis, ete., which oceur in temperate 
regions of both hemispheres, though not within the A 
Cirele, but which, if counted, would increase the number © 
identical species in the eastern and western hemispheres. ' 
oward the warmer regions of each continent the number 
of identical plants rapidly diminishes, and the proportion 
endemic species becomes very great. But in view of the 
marked similarity of the herbaceous vegetation of northern 
urope, Asia and North America, it seems only logical to & 
pect a notable proportion of identities between the trees 4? 
shrubs of boreal range, especially when, as in Betula and Sale, 
several species extend nearly or quite to the northern limits ° 
_ _ * J.D. Hooker, Trans. Linn. Soc., xxiii, pt. 2, 251-358; see also Gray, 
Mem. Am. Acad., n. s., vi, 377-449, and extract ‘‘Flora of Japan,” in St 
Pap. of A. Gray, selected by C. S. Sargent, ii, 124-141. 
