310 BOTANICAL GAZETTE [MAY 
the rock surfaces are not level, the soil made by lichens and 
mosses is washed into the crevices or into hollows made by the 
action of ice or water erosion. At once a herbaceous and 
shrubby vegetation springsup. Plants like huckleberries, golden- 
rods, Potentilla tridentata, Campanula rotundifolia, and the bear- 
berry gain a foothold in the crevices. These are followed by 
arbor vitae (Zhuwja occidentalis), the junipers, and the pines. ig. 
6 shows a rocky island in a bay near Marquette. At a distance 


Fic. 6.—A granite island in Lake Superior near Marquette. At a distance it 
appears destitute of ~~ growth. 
it looks barren of vegetation, but a closer view (jig. 7) shows 
that it is not altogether destitute of plant life. /%g. 8 is from a 
photograph of a larger island near by which shows a much higher 
type of vegetation, for here are found red and white pines. The 
weathering process is greatly aided by the prying action of roots. 
fig. 9 shows a red pine whose roots have split and raised a 
granite rock. 
One of the noticeable features of rock vegetation is its 
variety. Within the limits of a few square rods miniature repre- 
sentations of all the great plant societies are found. Near a 
roche moutonnée, as smooth and as barren of vegetation as the 
day the ice sheet left it, is a small depression containing a 
swamp, in which sphagnum moss and the cranberry are found ~ 
growing. Near by is a lichen society; this may grade into a 

