360 George E. Nichols, 



hogs, where, at the south end, there still remains a pond some 

 sixty feet long by twenty-five feet wide (Fig. 43). The filling 

 in of such a pond is accomplished through the intervention of a 

 floating mat, and the general features of mat formation are quite 

 similar to what the writer has described for Connecticut bogs 

 ('15, pp. 196-202). Its formation is brought about through the 

 combined activity of shrubs, sedges, and sphagnums. Very 



Figure 43. — Bog near mouth of Barrasois River; Nymphaea in fore- 

 ground ; sedge-shrub-sphagnum mat in middle distance ; bog forest in 

 center background. 



commonly the forerunner of mat formation is the cassandra 

 {Chamae daphne calyculata) . This shrub occurs both along the 

 shore and along the edge of the advancing mat and frequently 

 grows out several feet into the open water. Its relation to the 

 mat is similar to that of the steel framework to a concrete 

 building: it forms a skeleton upon which the sphagnum may be 

 supported. The necessity for such support will be pointed out 

 in the next section. Where, as is commonly the case, the cassan- 

 dra is followed by a dense growth of sphagnum, a mat is 



