456 . George E. Nichols, 



with Weber that even a mature raised bog is far from being in 

 a condition of permanent equihbrium. To quote Weber {op. cit., 

 pp. yy-y^) : "Die Teiche sind nach alledem ebenso .... 

 Symptome der bestandigen Veranderung, die die Oberflache des 

 Hochmoores unter dem wechselnden Einflusse erfahrt, den die 

 Witterung langerer Zeitraume auf die Vegetation und den 

 Boden ausiibt. Solange die natiirhche Vegetation vorhanden ist, 

 gleicht das Hochmoor gewissermassen eineni langsam pul- 

 sierenden und auf die ausseren Einfliisse in eigentiimHcher 

 Weise reagierenden Organismus." 



In brief summary of the successional relations of raised bogs, 

 as developed on essentially flat or undulating surfaces, it may be 

 stated that, in any given area, there may ensue a sequence of 

 stages, starting with a pioneer stage, passing progressively 

 through bog meadow and wet bog, and culminating in dry bog, 

 which latter constitutes the climax stage of the complete series. 

 But the series is not always complete. In an area occupied by 

 dry bog, either or both of the preceding stages may have been 

 omitted ; while, on the other hand, either of these two stages 

 may constitute locally an edaphic climax. The course of events 

 is dependent primarily on the activity of certain groups of 

 sphagnums and is conditioned by the presence of environmental 

 conditions suitable to their growth. In the course of a bog's 

 development, through the activity of the cushion- forming 

 sphagnums, ponds are formed which, by conserving the water 

 supply, bear a vital relationship to the bog's growth. It may be 

 added that the growth of a bog is not entirely vertical. As it 

 grows upward it spreads out laterally. A bog originating in an 

 edaphically favorable area may spread out in all directions, 

 eventually covering many areas which of themselves were not 

 favorable to bog development. In this way, as has been 

 repeatedly pointed out, a bog may invade an area occupied by 

 forest and bring about the destruction of the latter. Instances of 

 this sort have been frequently observed in northern Cape Breton. 



3. The Formation-types along Streams 



THE ASSOCIATION-COMPLEXES OF RAVINES AND FLOOD PLAINS 



The ravine associations of the hydrarch series here in the 

 highland, like those of the xerarch series, require no special treat- 



