Vegetation of Northern Cape Breton. 353 



C. THE ASSOCIATION-COMPLEXES OF UNDRAINED LAKES AND 



PONDS 



The association-types of permanent ponds. — Sink-hole ponds 

 commonly have no visible outlet and are practically undrained. 

 Aquatic vegetation as a rule is luxuriantly developed here, but 

 varies greatly in its floristic composition, even in neighboring 

 ponds. In one small pond, for example, Potamogeton natans is 

 practically the only species present; in another, Chara; in 

 another, Fontinalis gigantea; while in still another, Chara, 

 Fontinalis gigantea, and Potamageton pusillus grow inter- 

 mixed. Such ponds fluctuate more or less in level from season 

 to season and the marginal vegetation resembles that of periodic 

 ponds. 



Of particular interest, in view of their subsequent history, 

 are the undrained ponds in which originate peat bogs. The 

 water in these fluctuates very little in level from season to season, 

 and while the ponds may be small in area they are usually 

 fifteen or more feet in depth. Depressions of this sort are by 

 no means common near the coast, and most of those which were 

 discovered had already attained the bog stage in their develop- 

 ment. It is of interest to note, however, that the pioneer vege- 

 tation in and about these ponds is similar in most respects to that 

 of other ponds. The aquatic vegetation includes Nymphaea 

 advena, species of Potamogeton, and various aquatic mosses 

 and algae. Chara, however, seems to be rare or absent. In the 

 shallow water near the margin may grow Sparganinni 

 americanum, Eriocanlon septangulare, Carex Pseudo-Cyperus, 

 Potentilla palustris, and Lobelia Dortmanna. Along the more 

 or less mucky shores may occur herbaceous species, such as 

 Onoclea sensihilis, various sedges, Iris versicolor, Lysimachia 

 terrestris, Hypericum virginicum, and Lycopus americanus; 

 and shrubs, such as Myrica Gale, Alnus incana, Rosa nitida, and 

 Ilex verticillata. The most striking difference between these and 

 ordinary ponds is seen in the frequently luxuriant development 

 of various species of Sphagnum, the significance of which will 

 be pointed out later. The marginal shrubs here also commonly 

 include Chamaedaphne calycnlata and Kalmia angustifolia, both 

 of which are typical bog forms. 



The association-types of periodic ponds. — Periodic undrained 

 ponds scarcely differ in their vegetation from periodic well- 



