12 MICHIGAN SURVEY, 1908. 



specially that of the Balsams, encroaches upon the Cladonia society, 

 the Bearberry first becomes reduced in number, and is then replaced 

 by Aster macrophyllus, and a moss from the forest floor. The former 

 is perhaps the most striking and characteristic shade plant upon Isle 

 Koyale. The succession, or order of invasion on the ridge, from the Cla- 

 donia to the Juniper and into the BaJsam foi-est, is thus briefly shown 

 in the transverse section from the central ridge to its margin. This zonal 

 phenomenon, as will be seen later, is only an expression of the relative 

 rates of invasion, and is not a phenomenon separate from the normal 

 succession. 



The soil upon the top of the ridge is about two inches deep. It is 

 residual, supplemented by the humus from a now extinct crustaceous 

 lichen society (that of the Cladoni a -Bearhervy), and at its margins 

 by the Juniper, Balsam, Birch and Jack Pine leaves and debris and 

 further, to an important degi'ee, by the excrement of the numerous 

 Varying Hares which frequent the rock ridges. 



In the case of rock ridges which entend down to the beach and are 

 thus in direct communication with the shore drift, conditions exist 

 which show how such ridges may have been invaded by lichens from 

 two sources — the shore drift and the exposed beach itself — because of 

 the continuity of the rock habitat. Of course possibly another origin 

 is to be found in the fact that this ridge was itself once a beach. Ants, 

 grasshoppers and a few other Insects characterize this fauna, which 

 is limited in variety, but fairly abundant in individuals. The Hares 

 are abundant and form distinct paths or runways, as shown in Fig. 9. 



Station I, Substation 3. Balsanv-Wliite Spruce Fwest. This station 

 included the forest traversed by a blazed trail from near the south- 

 eastern part of Sta. I, 2, and extended northward to the clearing about 

 the light-house (I, 7), and beyond it to the north rock clearing (I, 2). 

 Most of the region occupied by the forest is of low relief, with an occa- 

 sional low rock ridge or hill. The dominant tree was the Balsam Fir, 

 with much Paper Birch and White Spruce. Where the forest was very 

 dense, especially if due to the number of Balsams, the ground was densely 

 shaded and there was almost no herbaceous ground cover ; but wherever 

 there was a small opening, due to a fallen tree, or where one had been 

 cut down, there was an abundant growth of Large-leaved Aster and 

 White-flowering Raspberry; and it was in the midst of such conditions 

 that young Balsams abounded. These were very characteristic plants in 

 such conditions. In msost cases ai thick layer of humus covered the 

 ground, but the tree growth was of small size. The common size of the 

 Balsam was about 4 inches, the larger ones reaching 8 to 10 inches. The 

 Birches averaged lai'ger, usually about 6 inches. No evidence of burns 

 were seen, but probably many trees have been cut from this vicinity, 

 because of its proximity to the lightrhouse, and the former Indian camp- 

 ground now occupied by the fishermen. The Balsam appeared to become 

 dominant at this place, as more young trees of this species were seen 

 than of any other. 



The fauna found in this forest was rather limited, and doubtless 

 great numbers of the insects which were taken in the clearing about the 

 light-house (I, 7), bred in the adjacent forests. This is particularly true 

 of the Cerambycids and other wood infesting beetles, the wood-boring 



