Fink: lichens of the northern boundary. 169 



study of them due to long experience, accounts for the fact that 

 this region about Rainy Lake City has furnished a larger num- 

 ber of lichen forms than any other in the state — 163. 



The collecting stations were Oak island and a few surround- 

 ing islands, Warroad, Beaudette, Emo, Koochiching, Rainy 

 Lake City, Kettle falls, Harding and Tower — also a few 

 plants were collected at Le Claire, and on the mainland near 

 Oak island. The islands possess the rock exposures and the 

 hard wood and the coniferous trees as well as the swamps of 

 certain other portions of the area studied and were found to be 

 fully as rich in lichen forms and to present no special distribu- 

 tional peculiarities, except the presence of a somewhat larger 

 per cent, of northern forms. Beaudette was the poorest field 

 visited as regards numbers collected and only furnished 102 

 forms. This is due to the presence of a vast cedar and tamarack 

 swamp with only a very few hard-wood trees and almost no 

 rocks at all. The swamp is unexcelled in richness of species 

 characteristic of such environment, but comparatively few other 

 lichens are to be found. Warroad presented little better con- 

 ditions in general, and had it not been for the finding of a single 

 rock exposure one half mile long, toward Roosevelt, would 

 have furnished few more species. This exposure of rock, said 

 to be thirty miles from other surface rocks, furnished many 

 of the Biatoras, JLecanoras, Biicllias, Cladonias, Umbilicarias, 

 and Rinodinas characteristic of such habitat and was surpris- 

 ingly rich in lichens for such an isolated area of rock. Oak 

 and other neighboring islands furnished 144 forms and War- 

 road, with the rock exposure mentioned, 130. At Emo on 

 Rainy Lake river, lichen-bearing rock exposures were not 

 numerous, and the number was 128. At Koochiching, at the 

 west end of Rainy lake, rock exposures became more plentiful, 

 and the number reached 145. The number for Rainy Lake 

 City is 163, for Kettle falls 129, for Harding 125 and for Tower 

 145. At Kettle falls and Harding a special effort was made to 

 study the woods and swamps more especially, so that the work 

 on the rock exposures was not thoroughly covered ; and it may 

 be said that the apparent differences in richness in lichens in 

 various portions of the area covered is almost wholly due to 

 differences in amount of rocky substrata, or to amount of work 

 done on them. 



One feature of the work that has added to the whole number 



