Fink: lichens of the northern boundary. 177 



Collema flaccidum Acn. 

 Leptogium lacerum (Sw.) Fr. 

 Leptogium tremelloides (L.) Fr. 

 Cladonia Ccespiticia (Pers.) Flk. 

 Baeomyces byssoides (L.) Schaer. 

 Biatora lucida (Ach.) Fr. 



B. Probably migrated from trees near by. 



Parmelia conspurcata (Schaer.) Wainio. 



Parmelia physodes (L.) Ach. ? 



Parmelia borreri Turn. var. rudecta Tuck. 



Parmelia caperata (L.) Ach. 



Physcia stellaris (L.) Tuck. 



Physcia speciosa (Ach.) Nyl. 



Physcia hispida (Fr.) Tuck.? 



Physcia obscura (Ehrh.) Nyl. 



Nephroma tomentosum (Hoffm.) Kbr. ? 



C. Species that have migrated from earth. 



Peltigera canina (L.) Hoffm. 



Peltigera aphthosa (L.) Hoffm. 



Similar formations were met elsewhere during the summers' 

 work, but were not carefully studied and would add nothing to 

 the list recorded above. The formation listed above lies along 

 some perpendicular rock exposure some twenty rods back from 

 the shore line and about a half mile from Rainy Lake City, 

 while the exposed rock formations, like the one first recorded in 

 this paper, may be found at many points along the lake shore, 

 and at a few places back from the shore, but here usually poorly 

 developed because of recent fires or the presence of trees- over 

 the rocks. The two formations recorded above are the extremes 

 for the region, and every gradation between the pure exposed 

 rock lichen formation and the mixed one in more shaded spots 

 may be found. The society listed last above was found on rocks 

 for the most part perpendicular, and it has been thought best to 

 give later another formation found here and elsewhere on more 

 horizontal rocks, more covered with humus. This formation 

 will be recorded as a Cladonia rangiferina formation of humus- 

 covered horizontal rocks. Attention is directed to it here lest 

 those familiar with the luxuriance of the Cladonias of the region 

 and not so familiar with our analysis should wonder why these 



