244 NICHOLS: THE VEGETATION OF CONNECTICUT 
formation of this region thando 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. 
The 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 amplexifolius, 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 splendens, Ptilium Crista-castrensis and Hypnum 
Schreberi 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 roseus Viola rotundifolia 
Actaea rubra Lonicera canadensis 
Oxalis acetosella - Aster acuminatus 
