MacMillan : shores at lake of the woods. 1005 



Flat shores of rock. If crevices are absent the population 

 consists of lichens and mosses. The action of surf regulates 

 somewhat the distribution, and upon such shores algal pools 

 like those previously described for front strand are common. 

 The wet area nearest the lake may be termed the Endocarpon 

 zone, from the prevalence of lichens of this genus; the zone 

 next inland as the Biatora zone, and the one farther yet toward 

 the country-line as the Cladonia zone. 



Rounded shores of rock. The same zones are established here 

 except that they are not so broad. Generally a growth of Endo- 

 carpon just at the water's edge is succeeded within a few inches 

 by the other two, so that Gladonias, which, with Stereocaulon 

 paschale, grow in great profusion on all such shores, occur 

 within a couple of feet of the high water mark. Yet the ex- 

 posure of the shore, as regulating possible surf -activity, has 

 much to do with the breadth of the zones and the interesting 

 observation may be made that on sheltered islands with smooth 

 rock shores the Cladontas grow much nearer the water's edge 

 than on exposed shores. Where the rock is particularly 

 smooth there is greater difficulty in the establishment of the 

 Cladonia zone, and its place is in many cases occupied by a zone 

 of Umbilicarias Such an Umbilicaria formation is beautifully 

 developed on the western end of the Isle de Massacre. In addi- 

 tion to the lichen flora some small lithophytic mosses are es- 

 tablished upon smooth rock surfaces, but since the mosses are 

 almost always crevice plants they may be better considered 

 later. In the background of Plate LXXVIII a rather precipit- 

 ous rocky shore is shown with few crevices near the lake, and 

 here the zonal distribution of the lichens was apparent. 



In general, since the lower plants are not particularly a mat- 

 ter of study in this paper, it may be said that flat or rounded 

 smooth rocks offer so little foothold to plants that, although 

 the conditions are favorable to zonal distribution, yet only 

 lowly plants partake of it and the account need not be pro- 

 longed. It is sufficiently apparent that differences of expos- 

 ure, of contour, of color, degree of hardness, chemical com- 

 position, illumination and irrigation must produce differences 

 in the lichen population, but that a fundamental tendency to 

 appear in zones is nevertheless discernible underneath the va- 

 riety induced by the differences mentioned. 



