ECOLOGY OF ISLE ROYALE. 219 



In the smaller lakes, especially those nestled in depressions, the 

 surrounding forests protect their surfaces from vigorous wind action 

 so that there are practically no waves at all to check the encroachment 

 of vegetation along the lake margins. 



That the slope of the shore, in the case of protected lakes, has much 

 to do with retarding or assisting the encroachments of plants is self 

 evident. The Isle Eoyale lakes of the protected class show numerous 

 examples where the plant zone is much farther advanced on the gently 

 sloping side than on the opposite one with a more abrupt slope. 



A typical example of a lake midway in the process of capture is 

 Sumner Lake. This lake, which is roughly one-half mile long and one- 

 third as wide, with its long axis nearly east and west, has already 

 been captured at its east and west ends. Had its north and south 

 borders been less steep the entire lake would doubtless have been 

 covered ere this. This lake has an outlet into Conglomerate Bay, but 

 at its west end it receives a small creek. The west end is covered by 

 a bog carpet still so young and elastic as to render the crossing of it 

 diflScult. Along the more abrupt sides, and connecting the bog carpet 

 at the ends, was a narrow, irregular zone of Calla palustris and Iris 

 versicolor, with the Mcnyanthes (Euckbean) and Comarvmv paliistrc 

 (Marsh cinquefoil) mixed in places. Parts of this zone, where the shore 

 is less steep, were closely backed up by willows, Cornus stolonifera, and 

 Alniis incana, thus giving to the marginal zone the aspect of a swamp 

 rather than of a bog. Growing on the wet bog carpet at the ends were 

 tlie Rarracenia purpurea, Drosera rotundifolia, Drosera intermedia, Men- 

 yanthcs trifoUata, Comarum palustre, Drosera linearis (the latter two 

 in wetter places generally than the former), Oxycoccus oxycoccus, 

 Hahcnaria psycodes, Hahcnaria dilatnta, Pogonia ophioglossoides, TJtri- 

 ciilaria minor (wetter parts), Campauul-a aparinoides, Scutellaria galer- 

 icula, Cicuta hulbifera, Triadeiimn virginicum, Parnassia- palustris, 

 SoUdago neglecta, etc. 



A word in passing in regard to the "false bottom'' of Sumner Lake, 

 for in no place on the island was this better shown. In paddling around 

 the open part of this lake on a raft it appeared in places that the water 

 was only 6-10 feet deep. This was a matter of surprise since even a 

 raft's length from the shore we could not touch bottom with our 15 foot 

 pole. Further investigation showed a "false bottom" in various parts 

 of this lake. This was composed of the flue, disintegrated remains of 

 leaves and other light organic material. In places there were great 

 breaks in this "false bottom," doubtless due to the escape of gases 

 which has lifted this fine, ooze-like material from a greater depth; and 

 through these breaks one could look down several feet through the 

 brownish colored water. While this "false bottom" was so tenuous 

 that a pole could be thrust through it almost as easily as through the 

 clear water, it seemed to play an important part in the distribution 

 of patches of GastaUa odorata (White Pond Lily) so abundant on the 

 surface of the lake, and also served to call attention to the manner in 

 which this material assists in lake filling. 



An area illustrating the final stage of bog covering was examined 

 at the end of the cabin trail from our Siskowit Bay camp. In this 

 sphagnum bog (V, 5), containing 80-100 acres, all has been covered 



