NICHOLS: THE VEGETATION OF CONNECTICUT 249 
If the erosion is slight enough to allow a vegetation carpet to 
develop, a high degree of luxuriance may be attained. In fact, 
Tavine conditions are usually extremely favorable for plants, after 
the initial stages have passed. In a comparatively few years 
the vegetation leaps, as it were, by bounds through the herbaceous 
and shrubby stages into a mesophytic forest, ... . Nothing 
shows as well as this the brief period necessary for a vegetation 
cycle in a favored situation as compared with an erosion cycle,” 
In Connecticut, clay ravines are much less frequent than are 
those in rock. They exist on a small scale in many parts of the 
Central Lowland, especially along the Connecticut River from 
Glastonbury to Windsor Locks, but elsewhere they are rare. 
Nowhere in this state are the successive changes in vegetation 
which accompany the development of a clay ravine so clearly 
shown as in the area described by Cowles, an area which the writer 
has visited on several occasions. So far as it has been possible to 
compare, however, the observations recorded in the Chicago 
region seem quite applicable to conditions in Connecticut. 
PRE-EROSION TOPOGRAPHY AND ITS BEARING ON THE PHENOMENA 
OF SUCCESSION IN Rock RAVINES 
‘From the standpoint of dynamic plant geography our land 
areas are divided into two well-marked categories: on the one 
hand is the erosion topography which is characteristic of the erod- 
ing and depositing phases of present streams and shores, and on 
the other hand is the preérosion topography which is characteristic 
of those areas that have not as yet been invaded by erosive 
forces.”"* To this latter category, speaking from the standpoint 
of the succession of plant associations, belong rock ravines. For 
while it is conceivable that, just as in the case of clay ravines, the 
topographic changes which accompany the development of rock 
ravines might react on the vegetation, yet such changes are brought 
about with such extreme slowness that their effect on plant life 
may be regarded as practically negligible. Whatever changes in 
the nature of ravine vegetation may have taken place in the past 
have probably been associated not only with topographic changes 
but with climatic changes as well; and the same will very likely 
* Cowles, H. C. Bot. Gaz. 51: 172, 173- I9gtt. 
