Vegetation of Northern Cape Breton. 441 



the sphagnums thrive most luxuriantly and grow most rapidly 

 and that the surface of the bog tends to be built up the fastest 

 and to the greatest height. Farther away from the pond, at 

 least during drv' spells, the water supply is less abundant, so that 

 the rate of upward growth is slower and the height limit lower 

 than in the more favorable central portions. The conditions, 

 however, are not always as simple as are here suggested. 

 Especially are complexities introduced through the development 

 of ponds which are a result rather than a primary cause of- bog 

 development. Ponds of this "subsequent" type, as will be shown 

 presently, are even more generally associated with raised bogs 

 than are ponds of the "antecedent" type, like those just described. 



/S. Development of Raised Bogs over Flat or Irregularly 

 Undulating Rock Surfaces 



Perhaps more commonly than not, in northern Cape Breton, 

 the rock floor which underlies a raised bog is essentially flat or 

 else irregularly undulating : at any rate there are no rock basins 

 capable of holding any appreciable amount of water. In the 

 development of raised bogs in situations of this description, 

 three more or less definite stages can frequently be distinguished, 

 which may be designated respectively the Bog Meadow stage, the 

 Wet Bog stage, and the Dry Bog stage. Owing largely to local 

 variations in topography, the rate at which bog formation has 

 progressed and the degree to which the raised bog climax has 

 been approached varies greatly. All stages in the succession, 

 which under favorable conditions culminates in the formation of 

 the typical raised bog association-type, may be found, and, 

 locally, any of the three types just mentioned may constitute an 

 edaphic climax. Through the study and comparison of a large 

 number of such areas, the general course or courses of develop- 

 ment and the ecological relations of the association-types involved 

 have been quite satisfactorily worked out. In the following 

 account, attention is first directed to the chief features, vege- 

 tational and otherwise, of the respective stages, after which their 

 relation to one another and to bog development will be discussed. 



The hog meadow association-type. — As stated earlier, the sur- 

 face of the tableland comprises a series of low, rounded hills, 

 which rise to a rather uniform height and are separated by 



