Vegetation of Northern Cape Breton. 



377 



well exposed above its surface. The explanation for this unusual 

 condition seems to be this. The pines formerly grew on a low, 

 sandy, pondward extension of the present spit. Through some 

 shifting in the tidal currents the sand was eroded away from 

 around the bases of the trees, and subsequently, presumably 

 as the result of further shifting in the current, deposition has 

 succeeded erosion and the salt marsh has been built up. The 

 active erosion of the sand spit which is now taking place along 



Figure 45. — Salt marsh at South Pond, Aspy Bay ; scattered stumps in 

 marsh; see text. 



certain other sections of the shore upholds the plausibility of 

 the explanation just given, and excavation of the muddy deposit 

 about the stumps shows beach-sand at a depth of scarcely a 

 foot below mean low tide level (in this connection, see also 

 Harvey '18). 



The pioneer association-type. — The mechanics of salt marsh 

 formation need not be detailed here : suffice it to say that it is 

 accomplished through the combined activity of plants and physio- 

 graphic agencies (see in this connection, Davis '10). In north- 

 em Cape Breton, as in salt marshes along the New England 

 coast, the pioneer stage in the salt marsh successional series is 



