Fink: lichens of the northern boundary. 183 



Pannaria rubiginosa (Thunb.) Delts. 



Pannaria rubiginosa (Thunb.) Delis, var. conioplea Fr. 



Pannaria leucosticta Tuck. 



Leptogium myochroum (Ehrh.) Tuck. 



Leptogium pulchellum (Ach.) Tuck. 



Lecanora subfusca (L.) Ach. var. allophana Ach. 



Lecanora pallescens (L.) Schaer. 



Pertusaria communis DC. 



This swamp at Boucherville was studied on one of the trips 

 out from Emo, a few miles farther up Rainy river. The 

 landing called Boucherville is on the Canadian side, and the 

 swamp lies a few rods west of the few houses and along the 

 river bank. Most of the surrounding land is now cultivated ; 

 and what were the original surroundings was difficult to deter- 

 mine in the short time at hand, nor was note made of conditions 

 farther down stream. But to all intents we entered a small 

 cedar swamp and there found in fifteen minutes all of the 

 plants of the above formation, which is the most characteristic 

 one yet found on the cedars. The number of plants is the 

 largest seen in such formations in any one place, but all of the 

 genera, except Pyxine, and about two thirds of the species may 

 be found in almost any cedar swamp of the region. In the 

 present formation the Cetrarias and Pannarias are as charac- 

 teristic of the society as any of the Stictas. Cetraria lacunosa 

 Ach. and Pannaria rubiginosa (Thunb.) Delis, are especially 

 fond of the cedars, and the last three plants of the list are 

 scarcely less so. In the presence of tamaracks the formation 

 is still reasonably distinct, though it must not be understood that 

 there are here recorded all the lichens that occur on cedars ; and 

 when tamaracks are near by or mixed with the cedars, members 

 of the last formation come in and confuse to some extent. The 

 pecular thing is that while the lichens of the tamaracks wander 

 to the cedars in mixed swamps, those more characteristic of the 

 cedars are very seldom seen on the tamaracks. An attempt 

 was made at the similar formation at Bemidji. The further 

 study confirms the existence of such formations, but also a 

 comparison of the two lists proves that the first results were 

 very meager. The Pannarias and Leftogiums, as is well 

 known, like moist and shaded habitats, and are possibly quite 

 as numerous on certain hard-wood trees when mixed with the 

 cedars in swamps. This was noted especially in swamps about 



