244 Nichols: The vegetation of Connecticut 



formation of this region than.do the forests on the adjoining uplands. 

 In a large measure this fact of course is due to the exceptionally 

 favorable conditions of environment under which they have been 

 developed. But there are other contributory causes which, while 

 they have nothing to do with the development of these forests, 

 may at least be partly responsible for their perpetuation. Thus, 

 on account of their comparative topographic isolation, ravine 

 forests may be largely immune from the fires which frequently 

 devastate the surrounding uplands, while by reason of the diffi- 

 culty in removing the timber they offer little temptation to the 

 lumberman. 



Tlie Boreal Aspect of the Vegetation in Rock Ravines. — ^A few 

 locally rare Canadian plants, such as Lophozia alpestris, Lophozia 

 attenuata, Gymnostomum rupestre, Polytrichum alpinum, Lyco- 

 podium Selago, Streptopus amplexif alius , and Viola Selkirkii have 

 been collected only in rock ravines. From an ecological stand- 

 point, however, it is the mass-effect of the vegetation rather than 

 the occurrence of isolated species which is significant. Many 

 of the bryophytes, which have already been referred to as being 

 largely restricted to rock ravines in Connecticut, are much more 

 generally distributed farther north. But even if these rock-face 

 and crevice forms are ignored, the stamp of the north on the 

 vegetation here is unmistakable. The predominant trees of ravine 

 forests are usually species of northward range. The bryophytic 

 flora of these forests — the mossy carpet of Bazzania trilobata, 

 Hylocomium splendefis, Ptilium Crista-castrensis and Hypnimi 

 Schreheri which frequently covers the forest floor — likewise is 

 strongly suggestive of the north. In Sage's Ravine, and doubtless 

 elsewhere, masses of Sphagnum, grow high up on the slopes — a 

 common phenomenon in the Maritime Provinces of eastern 

 Canada. Moreover, in Connecticut, many vascular plants charac- 

 teristic of the north woods, while by no means confined to this sort 

 of habitat, attain their optimum development in rock ravines. 

 As representative of this latter group of species may be cited : 

 Phegopteris polypodioides Acer pennsylvanicum 

 Taxus canadensis Acer spicatum 



Streptopus roseiis Viola rotundifolia 



Actaea rubra Lonicera canadensis 



Oxalis acetosella Aster acuminatus 



