1903 ] VEGETATION OF THE BAY OF FUNDY MARSHES 297 
round about can carry them readily to every part of it. Under 
these circumstances there is not, nor can there be in the marsh- 
land, any development of extreme adaptations, much less of new 
types. What happens is this—the ecological conditions here 
prevailing select from the great mass of forms which are con- 
stantly brought to them by natural modes of dissemination, the 
particular forms that happen to be best adapted to those con- 
ditions, rejecting, by suppression, all others. Further, as I 
believe, having selected the best adapted, their adaptations are 
in such a basin improved and intensified, so that these forms are 
being distributed from the basin in a better adapted condition 
than they enter it. Probably it is a general rule that the larger 
and more isolated the basin the more the tendency to develop 
peculiar types; the smaller and less isolated the basin, the more 
is it a case of selection of forms brought constantly into it and 
their improvement, such small basins serving as centers of dis- 
tribution of better adapted forms. The ecological interest of 
these marshes lies, not in any peculiar adaptations they show, 
but in the perfection with which they exhibit many phenomena 
of adaptation. 
Summary of the ecological factors; the responsive type of 
vegetation. 
The various physical features we have just considered consti- 
tute a set of conditions to which the vegetation must conform. 
Since no development of a special vegetation to fit them is 
possible, we ask what forms of the plants of this region do come 
nearest to fitting those conditions and hence actually occur there. 
So far as the general climatic conditions are concerned, the 
responsive type for this region, as I have elsewhere shown,* is 
a mixed mesophytic forest, such as actually occurs on the neigh- . 
boring uplands. But on the marshes there comes in another 
factor which is of the first importance and is prepotent or deter- 
minative, namely, the peculiar soil. This requires that the marsh 
Leetiige shall be such as has a superficial or very slender root 
The vegetation of New Brunswick as a whole I have considered in Bull. Nat. 
fies Soc. New Bruns. 5:52. ‘ 
