1012 MINNESOTA BOTANICAL STUDIES. 



It is also found at Lake of the Woods as the typical "inner 

 shrub" on dome-shaped islands, as described by me elsewhere, 9 

 and can not be regarded as a pure talus-type of plant forma- 

 tion. 



V. Betula talus-slopes. Growths of Betula papyrifera 

 sometimes occur on fine-talus, although usually the soil- 

 content is so considerable that the shores are better described 

 as humus shores. Yet Betula woods upon some of the islands 

 mark the fine-talus as sharpiy as Populus or Finns divaricaia 

 woods mark the coarse talus. 



VI. Pinus resinosa talus slopes. This species of Pine, the 

 "Norway pine" of Minnesota loggers, does not commonly grow 

 upon shores at Lake of the Woods, but is rather a back country 

 plant. Isolated individuals occur in various localities, in 

 crevices, on the strand, on dunes and on coarse talus. Special 

 colonies have been noted in three instances on fine talus slopes, 

 The exposure was slight, the slope gentle and the admixture 

 of soil considerable. 



Without extending the examination of coarse and fine talus 

 farther it may be observed that while coarse talus gives slight 

 opportunity for zonal distribution, fine talus, after the sufficient 

 lapse of time offers an area suitable for zonal distribution. 

 This is especially the case if the slant of the bed is gradual 

 and the admixture of soil such as to bury the talus-fragments 

 in a homogeneous mass of humus. A large number of transi- 

 tion types, mixed types, compound and irregular groupings, 

 may develop upon talus areas. The age, coarseness, slope, 

 extent, exposure, drainage, off-shore conditions of the bottom, 

 chemical composition of the talus blocks, juxtaposition of the 

 blocks, percentage of interstitial deposits and their character, 

 and back country biological conditions all influence and deter- 

 mine the nature of the talus population. 



BOULDER SHORES. 



Ecologically coarse boulder shores do not differ strongly in 

 themselves from coarse talus, nor fine boulder shores from fine 

 talus. But the conditions of their development are sufficiently 

 different to expose them, when formed, to a different set of 

 influences. While talus shores may occur in quiet secluded 

 regions of the lake, the boulder drift is found principally on 

 very open shores where there is strong wind and surf activity. 



(9) aiacMillan. Distrib. of Plants, etc. Bot. Gaz. 22 :21«. 1S96. 



