Vegetation of NortJicrn Cape Breton. 375 



concerning' which brief mention has ah'eady been made in dis- 

 cussing the vegetation of rocky sea bkiffs. In the remarks which 

 follow, attention is restricted to the associations along depositing 

 shores. These are conveniently treated under three heads : the 

 association-complexes of salt and brackish lakes and ponds, the 

 association-complexes of salt marshes, and the association- 

 complexes of brackish marshes. 



b. THE ASSOCIATION-COMPLEXES OF SALT AND BRACKISH LAKES 



AND PONDS 



The most prominent constituent of the aquatic flora in salt 

 lakes and ponds is the eel grass {Zest era marina) which com- 

 monly grows in great luxuriance, covering large areas of bottom 

 between approximately mean low water mark and a depth of 

 several feet below. Ecologically the eel grass fulfils an impor- 

 tant function in that, by its interference with tidal currents, it 

 stimulates the deposition of silt and the consequent upbuilding 

 of the bottom. Associated with the eel grass, but seldom attain- 

 ing any great prominence, usually grow the sea lettuce (Ulva sp.) 

 and other algae, which may either form a loose covering over 

 the sandy or muddy bottom or grow attached to the eel grass. 

 Another seed plant found here is Ruppia maritima. In Middle 

 Harbor (Aspy Bay), to select a concrete example, this plant is 

 not at all conspicuous toward the outlet, but in the shallow 

 water about the head of the harbor, in company with Potamoge- 

 ton pectinatus, it completely covers the muddy bottom with a 

 prolific growth. The presence here at the head of a sizeable 

 stream may account for the abundance of the Ruppia in this 

 vicinity, although this plant is by no means confined to brackish 

 water. In Cold Spring Harbor, Johnson ('15, p. 26) says that 

 Ruppia is most abvindant in areas of "soft bottom, bare of Ulva, 

 and usually protected from currents and waves." It is worthy 

 of note, however, that in brackish ponds, in northern Cape 

 Breton, the bulk of the aquatic vegetation consists of Ruppia 

 and Potamogeion pectinatus. 



The shores of salt and brackish ponds may be occupied by the 

 salt or brackish marshes which will be described presently, or 

 they may be merely muddy or gravelly. Gravelly shores ordi- 

 narily occur in more exposed situations than muddy shores. The 

 conditions which prevail on gravelly shores may be illustrated 



