880 THE AMERICAN NATURALIST. [Vor. XXXIX. 
an extension of the Northeastern Conifer forest. Probably it 
should be regarded as a subcenter, because of the large number 
of endemic forms present, and because many other species there 
attain their greatest development. There, it has been shown 
(Cowles, : o1b) that the pine stage is followed by an oak society, 
which in turn gives way to the climax deciduous forest. This 
seems to correspond with the succession in certain parts of the 

Q^ | } NS P 
2 ES. | 
j jo 
cys. ges 
m yy" 
PEN > 2 TJ 
; echinata 
d - 
(ue \ ; d ‘Pinus taeda 
1 1 2E " Se 
x : i oe : Pinus palustris} 
N Pinus heterophylla 
nn A Y a x Pinus glabra 
b ; Pinus glabra 
“Pinus echinata 
i-a Chamaecyparis thyoides 
N “Pinus tae 
Pinus taeda n 
N 
Pinus palustris” 



* v an 
eade 
Fic. 4.— Map sho 
wing distribution of several trees belonging to the Southeastern Conifer 
forest center, Ch paris thyoides i inih oat ; the pi 
Ath th ti 

es, 

f Pinus glabra, belong to the climax forest. 
lower peninsula of Michigan, where the pines and the oaks both 
occur. Both localities are intermediate between the same two 
forest centers, and such a correlation is to be expected. The 
earlier stages in the succession are dominated by the Northeast- 
ern Conifers, while the last two are parts of the Deciduous 
forest center. | 
Furthermore in such intermediate regions, we may find two - 
