Vci^ctation of Northern Cape Breton. 383 



abundance of which "prevents the salt water from really pene- 

 trating it." In such situations, therefore, many upland and 

 fresh swamp plants which can stand more or less inundation 

 of their shoots with salt water but which cannot endure salt 

 w^ater around their roots are enabled to push down to much 

 lower levels than usual, even growing below mean high tide 

 level. This explanation is doubtless the correct one, and the 

 line of demarcation between halophytic and non-halophytic 

 associations is always sharper along dry than along wet shores, 

 although even here non-halophytic plants frequently invade areas 

 which are subject to tidal overflow. 



Of peculiar interest in this connection is the occurrence of 

 bryophytes in situations where they must necessarily be more 

 or less exposed to the influence of salt water. In northern Cape 

 Breton, for example, Chrysohypnnm stcUatnm commonly 

 grows quite abundantly on the wet soil of brackish meadows, 

 in company with such vascular species as Triglochin pahtstris 

 and Ranunculus Cymhalaria, and the sphagnums sometimes 

 occur in similar situations. Sphagnum palustrc and Bryum 

 incUnatum have been collected on exposed sea cliffs well within 

 reach of storm waves, while Bryum fallax thrives around 

 the edges of salt ponds. From these and similar observations 

 elsewhere, there seems little question that while as a class the 

 bryophytes may be regarded as halophobous, many of them are 

 capable of existence in habitats where, periodically at any rate, 

 they are bathed in brackish or salt water. 



D. Secondary Formations of the Hydrarch Series 

 Formation-types resulting primarily from Human Activity 



ASSOCIATION-COMPLEXES DUE TO VARIOUS AGENCIES 



In SO far as the association-types of lakes and ponds are con- 

 cerned, the effect of human activity has been negligible. The 

 vegetation of swamps has been variously modified, but it is only 

 occasionally that it has suffered as severely as that of uplands. 

 This state of affairs, in the main, is easily explained by the fact 

 that in this climate, with its abundant atmospheric precipitation, 

 the swamps, for the most part, are of comparatively little value 

 from the cultural standpoint. Instances of a more or less pro- 

 nounced change in swamp vegetation from its original character 



