ECOLOGICAL SUCCESSION OF MOSSES 



207 



tion. Chamaedaphne persists however, possibly aided by the 

 germination of new individuals upon the moss itself. A new 

 group of plants now appears, which is destined finally to cause 

 the death of the sphagnum. First are relatively insignificant 

 species such as the Cranberry, Creeping Snowberry, Round- 

 leaved Sundew, and others. Most important is the Labradoi 

 Tea (Ledum groenlandicum Oeder), which becomes established 

 upon the highest portions of the sphagnum masses and whose 

 root system is strictly confined to them. Its influence lies in the 



Fig. 4 Bog on Raspberry Island. Carex limosa and Chamaedaphne calyculata 

 buried by sphagnum which has invaded the sedge mat, and keeping pace with 

 the growth of the moss by upward elongation. 



effective shade which it casts upon the light requiring sphagnum, 

 and the great amount of waste which falls from it and accumulates 

 upon the surfaces beneath. Accompanying Ledum or often 

 preceding it, and sometimes nearly as important, are several 

 mosses: Polytrichum strictum Banks, Aulacomnium palustre (L.) 

 Schwaegr., and Calliergon Schreberi (Willd.) Grout, in order of 

 their usual first appearance. Young plants of these species 

 start among the sphagnum heads and spread over the mass in 

 all directions. Stoppage of upward growth of the latter moss 

 follows as a necessity. Along the edge of the bog forest, at the 



