ECOLOGY OP ISLE ROYALE. 27 



This ground cover was not limited to the swamp, but invaded 

 the Balsam-Spruce forest in large billow growths, such as is 

 shown in Fig. JfJ^. In other places the undergrowth and ground 

 cover of . the Balsam-Spruce forest apparently invaded the swamp, as 

 was seen by the intermingling of the two plant societies. Here- 

 there is a mat of the Sphagnum and Labrador Tea intermingled 

 with Ground Cornel, Clmtonia torealis and young Balsams. As 

 in Fig. 4^i- this might also be interpreted to mean an invasion of the 

 Balsam-Spruce forest by the swamp ; but the vigor and dominance of the 

 Balsam society favors the interpretation that this is an invasion of the 

 swamp by the' Balsam society. It is not surprising that along such a 

 tension line either society may dominate at times. 



The fauna of this bog consisted of a Garter Snake {T. sirtalis), found 

 near the small brook flowing into the western or upper end of the bog. 

 Here algo was found Eyla piclceringii, Rana damitans, and R. 

 cantabrigensis, and a water strider, Gerris, running on the surface. In 

 the Cassandra and Sphagnum hummock zone were found the grasshop- 

 pers, Mecostethus lineatus, Melanoplus extremus, and Stenobothrus 

 eurtipermis.' Nearer the central lilypond, among the sedges and Cas- 

 sandra, were found the dragon flies, Tetregoneuria spinigera, Aesohna, 

 LeucorMnia hudsonica and Sympetrum oitrusum, and the spider Epeira 

 patagiata. Through the central area of the bog the stream was only 

 indicated by the parting of the sedges, but at the lower or eastern 

 end it again became well defined, and contained the small Stickle- 

 back, Eucalia inconstans. Beetles taken from this bog were Haliplus 

 ruficollis, Hydroporus tristis and Agahus congener. The molluscs were 

 represented by the small bivalves, Pisidium. 



Station V, Substation 6. South Shore of SisTcowit Lake. This sit- 

 uation is simply the end of the trail through the forest, and marks the 

 location of some collecting in the lake. The shore is rocky, with rather 

 low and overgrown banks. 



Station V, Substation 7. The Haytown Trail. This trail begins al- 

 most directly opposite the outlet of Siskowit lake, where a large White 

 Pine has been marked "36 W. 65 N., 19 E." This area has been burned 

 over, but farther inland the blaze on the older trees enables one to follow 

 the trail. The course is shown by Lane, ('98, PI. XI), but we examined 

 it only to about the point where it is crossed by the outlet of Hatchet 

 lake, at which place there was a Tamarack swamp with very large trees 

 (V, 8). After crossing the burned area near Siskowit lake, this trail 

 passed through dense Arbor Vitae bogs and a large area of Balsam-Birch 

 forest. In general the area traversed was rather deeply covered with 

 soil and contained very few rock exposures, those observed probably 

 being due to fires. 



The general character of the upland forest, of mixed conifer and 

 hardwood, is indicated by the following list: Balsams, Birch and 

 Aspens (all about 10 inches in diameter), scattered Arbor Vitae (10 to 

 15 inches), a few scattered White Pines (about 3 feet in diameter), and 

 a few Hard Maples (some 8 inches). It is thus seen that the largest 

 abundant trees are the White Pine, Arbor Vitae, Birch, Hard Maple and 



