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, 

 ravine 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 preerosion 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. 1911. 



