SUCCESSIONS IN BOGS 31 



They induce the establishment of the intermediate stage, 

 the xerophytic formation. Frequently one or more phases of 

 the bog succession are omitted entirely, and various deviations 

 or intercalations occur; always, however, they are replacing one 

 another quite independently of climatic and topographic changes. 

 The succession of associations, like that of the displacement of 

 successions themselves, is a form of edaphic selection due to the 

 establishment of certain species and the exclusion of others. 

 The plants themselves are the most important factor in bringing 

 about the change. As the production of land by the activity of 

 the vegetation continues, concomitant with the organic changes 

 in the soil is the replacement of one type of vegetation by another. 



A. The bog meadow associations 



According to the preponderance of certain plant forms, two 

 types of bog meadows may be recognized: 



1. Vaccinium macrocarpon-Spagnum sp. association. The veg- 

 etation is diversified and rich in the variety of possible facies 

 and societies. The list of a fairly representative example of a 

 bog meadow would include Carex limosa, C. filiformis, Menyan- 

 thes trifoliata, Rynchospora alba, Dulichium arundinaceum, Poten- 

 tilla palustris, Eriophorum virginicum, Drosera rotundifolia, 

 Sarracenia purpurea and less frequently Scheuchzeria palustris. 

 In addition to this groundwork of plants are several species 

 of orchids, Scirpus, Juncus, Aster and various stragglers from 

 preceding associations and a number of invading migrants. 

 Parnassus caroliniana, Lobelia spicata, L. syphilitica, Chelone 

 glabra, Gentiana crinita, Campanula aparinoides are less common. 



The amount of mineral salts is of subordinate significance. 

 Lime in the soil does not prevent their growth, for cranberry r 

 sphagnum meadows were until recently extensive in counties 

 overlying the Niagara and Monroe limestone formations, and 

 on peaty substrata near springs the water of which is charged 

 with carbonate of lime. 



The type of peat is coarse in texture and conducts water readily. 

 With any alteration in the water level the mat of the cranberry- 



