430 George E. Nichols, 



Its original size has been reduced about one-half by the centri- 

 petal encroachment of the bogs which now surround it to a 

 variable width on all three sides. In the still open part of the 

 pond, the bottom seems to be completely covered by a soft, mucky 

 deposit which in places must be many feet thick. This deposit 

 without question has been formed almost wholly through the 

 accumulation on the floor of the pond of vegetable debris, which 

 in large part has been derived from the remains of aquatic seed 

 plants, mosses, and algae. In proceeding from the middle of 

 the lake toward the shore, the depth of the water gradually 

 diminishes, the mucky bottom sloping gently upward until, just 

 before the lakeward margin of the bog is reached, it nearly or 

 actually reaches water level. On the substratum thus produced 

 a mat has been formed, which has advanced from the shore out 

 into the lake as rapidly as the filling in process has permitted. 

 And in this connection considerable interest attaches itself to the 

 divergent courses of development which have ensued on two of 

 the three sides of the lake. 



Along one side a sedge mat has pushed its way out for a 

 distance of a dozen or fifteen feet from the original shore. For 

 the development of this mat three plants have been primarily 

 responsible, namely Carex filiformis, Rynchospora alba and R. 

 fusca, and these are still the predominant forms, practically the 

 only other species present being Utricularia corniita, Drosera 

 longifolia, and Sphagnum Pylaisei. The mat is flat and firm, 

 and, although it is but a few inches above ordinary summer water 

 level, one can walk dry-shod almost to its edge. 



Along the other shore the behavior is somewhat different. 

 The shoal water along the margin of the advancing bog is 

 occupied by an association made up very largely of the mosses. 

 Sphagnum pulchnim and Drc'panocladus Sendtneri. These are 

 present in sufficient abundance to form a low, wet substratum 

 upon which the sedges, Carcx filiformis and Rynchospora alba, 

 together locally with Andromeda, gain a foothold. Thus there 

 is formed a low mat which paves the way for further progress. 

 But subsequent development is not always the same. It may 

 follow one of two courses, and which of these it shall be seems 

 to depend very largely on which species of Sphagnum gains con- 

 trol over the situation. Along much of the shore 5". papillosum 



