14 MICHIGAN SURVEY, 1908. 



undergrowth of Balsam, Mountain Alder, and a ground cover of Large- 

 leaved Aster, and passed on through a belt of j'oung growth of Birch, 

 with the usual White-flowering Raspberry and Large-leaved Aster, Ficj. 

 12, and up the face of an escarpment to the crest of the ridge, Avhich 

 had a height of about 100 feet above the lake level. From the abundance 

 and characteristic growth of Jack Pines on this ridge, the station takes 

 its name. Part of the ridge has been burned over, as was shown by the 

 burned and fallen timber, but the part to which our attention was given 

 was apparently an original growth. The Jack Pine was scattered, and 

 largely occupied the depressions and the larger crevices. The ridge is 

 fairly flat topped, but is occasionally broken by transverse gullies, which 

 contain Aspens, Birches, etc. The surface of the lava has weathered 

 but little in some places, the original roche moiitancos surface 

 being very clearly preserved, and the planed glacial surface but little 

 eroded. Near the escarpment, however, disintegration and decomposi- 

 tion have been much more active, probably influenced in part by lake 

 waves at former levels, thereby developing a talus slope, composed of an- 

 gular blocks, and in some places forming a stony soil. All intermediate 

 stages are found between these two extremes. In addition to the large 

 amount of bare rock surface, and that covered by only a thin layer of soil 

 and vegetation, the shallowness of the soil is further evidenced by over- 

 turned trees. Fig. 13. This soil is of residual and organic origin, the 

 crustaceous lichens and the Cladonia-Beavberry society, and later the 

 Jack Pines, having contributed much to its formation. The excrement of 

 the Hares has also been an important factor in soil formation, and that 

 of the Lynx also, though to a much less degree. 



The process of weathering must be relatively rapid on this ridge, 

 because it is exposed to the winds at all -seasons of the year, and to the 

 marked seasonal and daily changes of temperature. The heat of the 

 noonday sun is excessive, and the radiation from the nearly bare rock 

 must be rapid, as it also is at night, so that the various influences con- 

 sequent to temperature changes are allowed full play. Weathering is 

 further favored by the irregularities of the surface, and the crevices, 

 which allow the accumulation and downward conduction of this moisture, 

 thus permitting the prying action of ice. 



In general, the succession of plant societiesi on this ridge appears 

 to be about as follows: Lichens are the pioneers on the rock surface, 

 and these may be of several species, Umhilicaria. and the crustaceous 

 and foliaceO'US forms. As a soil develops in the crevices or on the sur- 

 faces, these are followed bv Cladonin. Bearberry, Sibhaldiopsis tridentata, 

 Solidago, Diervilla diervilla (Bush Honeysuckle) ; and later, when the 

 soil becomes deeper, by Amelanehicr, Pruints pcnnsylraiiica (probably 

 dispersed to these ridges by birds) and Jumperws nana.. The presence 

 of the Small-toothed Aspen, willow and an occasional Birch probably in- 

 dicates the next society. In the shade of the Birches and Jack Pines 

 Solidago and Aster maorophyllu.'i occur, if suflicient soil is developed. 

 Prom the character of the vegetation in the ravines which traversed the 

 ridge, and upon the talus slope toward the bay, it is apparent that the 

 next society tends to be that of Birch and Aspen with some Balsam, 

 Pennsylvania Cherry. Mt. Alder; and a ground co\er of Large-leaved 

 Aster, Large-flowering Baspberi-y, Ground Cornel and Lycopodiiiw. It 



