MacMillan : shores at lake op the woods. 1017 



Apparently the character of plants established upon an 

 irregular rock surface is conditioned upon a great variety of 

 causes. The size of the soil pockets, their depth, their oppor- 

 tunity of accumulating moisture, their temperature and illumin- 

 ation, their proximity to or remoteness from the waves, their 

 exposure to winds, and, in short, all the ecologic factors enter 

 into the problem and the prediction of definite species in soil 

 pockets of known size and depth would be impossible, so much 

 influence would the surrounding and secondary causes exert. 

 Yet one could name a number of plants not to be found in such 

 pockets and could limit the prediction within bounds. Even 

 this would sometimes expose a novice to difficulties for very 

 unexpected plants occupy these little pockets on an irregular 

 rock shore. For example on Windigo island, near Flag island, 

 the pockets, two or three square feet in extent and two and a 

 half inches in depth, in granitic rock were occupied over a con- 

 siderable area almost exclusively by Sphagnun cijmbi folium, a 

 most unexpected locality. The plants apparently drew upon 

 adjacent trees of Pinus divaricata established in crevices, for 

 shade and for sluicing the rain water into their little hollows. 

 These miniature peat bogs upon high, wind swept rocks, I have 

 not happened to encounter elsewhere. In one of them several 

 individuals of Moneses and in another a plant of Kalmia had 

 become established. 



Whether the pocket vegetation shall be lichens, mosses, 

 herbs, shrubs or trees, depends much upon the depth of the 

 pocket, its drainage supply and the environmental factors. In 

 these soil pockets the incalculable factors of distribution, such 

 as the dropping of seeds by birds, or by the wind or by roam- 

 ing animals, are so important that the vegetation aspect of the 

 region is quite unpredictable in its details. In the foreground 

 of Plate LXXX, the Sacred Rock of the Lake of the Woods 

 Indians is shown. One observes the irregular surface. The 

 depressions are very shallow; thus small amounts of soil 

 develop and only small plants — grasses, mosses and lichens — 

 are shown. In the background a coarse talus slope, with 

 Populus vegetation, appears. In Plate LXXIX, on the other hand, 

 deep pockets have been formed over the rock surface and on 

 them a forest of Pinus strobus is established. Mingled with 

 this species are crevice trees of Pinus divaricata. The two 

 plates give a good idea of the influence of surface- contour of 

 the rock substratum upon the plant physiognomy of the region. 

 The difference between the two shores is essentially one of 

 surface contour. Other factors are slight as compared with it. 



