Fink: lichens of the northern boundary. 171 



Nephroma laevigatum Ach. var. parile Nyl. C. 



Nephroma tomentosum (Hoffm.) Neck. C. 



Lecanora frustulosa (Dicks.) Mass. C. 



Lecanora verrucosa (Ach.) Laur. var. mutabilis Th. Fr. 



Stereocaulon paschale (L.) Fr. C. 



Stereocaulon tomentosum (Fr.) Th. Fr. 



Cladonia deformis Hoffm. C. 



Cladonia digitata (L.) Hoffm. C. 



Cladonia amaurocraea (Flk.) Schaer. C. 



Basomyces aeruginosus (Scop.) DC. C. 



Biatora lucida (Ach.) Fr. C. 



Lecidea lapicida Fr. C. 



Lecidea platycarpa Ach. C. 



Buellia geographica (Pers.) Tuck. C. 



Buellia petraea (Flk.) Tuck. C. 



Buellia petraea (Flk.) Tuck. var. montagnaei Tuck. C. 



Buellia badioatra (Flk.) Kbr. 



Buellia concreta (Kbr.) Eck. 



Buellia obscurata (Ach.) Eck. 



Buellia concentrica (Dav.) Fink. 



Inspection of the lists for the two regions involved shows con- 

 clusively that the one first studied has a much larger proportion 

 of arctic and subarctic lichen forms ; for the proportion is ap- 

 proximately two to one, while the whole number of lichens is 

 considerably smaller. This is what had been anticipated, 

 though areas some fifty miles farther north were reached in the 

 study of the region treated in the present paper. As was stated 

 in the paper cited above,* it w r as not expected that the north- 

 western part of the state would give a large number of northern 

 lichens, and the number found is larger considerably than was 

 supposed to exist when the stud)'' was begun. Professor Con- 

 way MacMillan f has noted the difference between the sperma- 

 phytic floras of the two regions ; and we conclude from his 

 statements that the post-glacial change in flora has been more 

 rapid for the higher plants than for lichens, and that the lichen 

 flora of the region about Lake of the Woods contains a larger 

 proportion of northern forms than does the sperm aphy tic flora 

 of the same area. 



*Fink, B. 1. c, 233-234. 



f MacMillan, C. Observations on the distribution of plants along the shore 

 at Lake of the Woods. Minn. Bot. Stud. 1: 954. 1897. 



