ECOLOGY OF ISLE ROYALE. 25 



Figure 34 shows the marked dominance of p'ocimibens, which was not 

 abundant on the west slope. The plant life is more varied, with the 

 foliaceous lichens and bunches of coral-like Gladonia, ferns, grasses. Soli- 

 dago, and the willows and aspens in the crevices, Fig. 31. These forms 

 give a very different aspect to the pioneer society from that of one 

 composed of a Cladoma-procmniens mat. The open or patch like char- 

 acter of this society suggests that the retarded development of the 

 vegetational cover may be related in some way to the scarcity of J. 

 procumbens, which is such an excellent agent in soil formation. But 

 why this shrub should not thrive here is not known. 



Associated with these conditions were the snail Polygyra alholahris, 

 and the grasshopper Melanoplus fasciatus. The absence of the dense 

 mat, and less soil, greatly reduced the variety of animals frequenting 

 such conditions. 



Taking the station as a whole (V, 2), it is one of the most interesting 

 places seen on the island. The beauty of the variegated Gladonia mat, 

 the extensive area of the open habitat, the boreal character of the lichens, 

 the Saxifrage and many of the shells, the apparent completeness of the 

 preservation of the stages in the transformation from the lower beach 

 back to the forest, all combine to make this situation one of the most 

 interesting and important of those examined.* 



Station V, Suhstation 4. Trail through Balsam-Spruce Forest. This 

 station begins at the opening about camp (V, 3) and extends northwest 

 to the south shore of Siskowit Lake, opposite the eastern end of an 

 elongated island. The topography of the region traversed is one of low 

 relief, with only occasional low rocks, hills, or ridges, 15 to 20 feet in 

 height, and a few shallow and moist ravines. A thick layer of humus 

 covers the surface, except on the ridges. The trail first passes through 

 a forest of White Spruce, Balsam, Birch and scattered Tamaracks. 

 Among these trees are many fresh windfalls, due to the winds and the 

 shallow soil. In the more shaded portions the ground cover consists 

 of a dense growth of mosses, liverworts, Fig. 38, with Aster macrophyllus 

 in the less shaded portions. There are open patches 10 to 15 feet in 

 diameter scattered about through the forest, especially on low rock 

 ridges, which contain a growth of Gladonia, and illustrate the last stages 

 of the decline of the openings. 



In the moist depressions was found an abundance of Eound-leaved 

 Cornel, alder, and also Ground Hemlock, Mountain Ash, Balsam, White 

 Spruce, and the Ground Pine (abundant.) There were many fallen 

 amd decayed logs. In and characterizing the more open places, such as 

 were associated with large Birches, ai*e the Large-flowering Rasp- 



* This slope is very favorable for the study of the ecological distribution of lichens, and at this point 

 attention is directed to some papers on lichen societies by Professor Bruce Fink, of Miami CoUege. 

 These are the most important papers on this subject. 



1902. Ecological Distribution an Incentive to the Study of Lichens. Bryologist, 5, pp. 39-40. 



1903. Some Common Types of Lichen formations. Bull. Torrey Bot. Club., 30, pp. 412-418. 



1903. Some Talus Cladonia Formations. Bot. Gaz., 35, pp. 195-208. 



1904. A Lichen Society of Sandstone Riprap. Bot. Gaz., 38, pp. 265-284. 

 Contributions to the Study of Lichens of Minnesota: 



I. Lichens of the Lake of the Woods. Minn. Bot. Stud., 1, 1896, pp. 693-701. 



II. Lichens of Minneapolis and Vicinity. Minn. Bot. Stud., 1, 1896, pp. 703-725. 



III. The Rock Lichens of Taylors Falls. Minn. Bot. Stud., 2, 1898, pp. 1-18. 



IV. Lichens of the Lake Superior Region. Minn. Bot. Stud., 2, 1899, pp. 215-276. 



V. Lichens of the Mirmesota Valley and Southwestern Minnesota. Minn. Bot. Stud., 2, 1899, 



pp. 277-329. 

 VI. Lichens of Northwestern Minnesota^ Minn. Bot. Stud., 2, 1901, pp. 657-709. 

 VII. Lichens of the Northern Boimdary. Minn. Bot. Stud., 2, 1903, pp. 167-236. 

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