238 MINNESOTA BOTANICAL STUDIES. 



bank lake, which are somewhat farther north, are almost 

 entirely devoid of such species. A third factor is increase in 

 elevation. The influence of elevation has been discussed in 

 considering the Misquah hills and the Sawteeth mountains. 

 Concerning cold lake winds and elevation, it is significant that 

 of the 25 arctic and subarctic species found only in one place, 

 16 are found at stations along the lake, and that of the remain- 

 ing 9, 5 are found in the Misquah hills, the region of highest 

 elevation. Thus all but 4 of these 25 species were collected 

 where one or both of these factors have most influence. 



It is not possible to state just which ones of the many species 

 found either in central or in northeastern Minnesota and not in 

 the other area would be of most interest in studying the territory 

 lying between the two regions. Of course, the foliaceous and 

 fruticulose species are most easily found, and some of these are 

 most likely to be collected. I may add that interest would 

 centre chiefly about species which are common and give char- 

 acter to the flora in one of the two areas and are not found in 

 the other. Not attempting to select from some 150 species col- 

 lected in the Superior area and not farther south in the state, I 

 will name, from 27 or 28 species found to the south and not to 

 the north of the unexplored area, Theloschistes concolor (Dicks.) 

 Tuck, and Physcia granulifera (Ach.) Tuck, as two species 

 that any botanist can soon learn to distinguish in the field, 

 which are common in the south half of Minnesota and not 

 known farther north in the state, and whose distribution be- 

 tween Minneapolis and Two Harbors would be of special inter- 

 est. Nearly all of the remainder of the 27 or 28 species are 

 either infrequent or rare about Minneapolis, are confined to sub- 

 strata not existing in northeastern Minnesota, or are so incon- 

 spicuous as to render their study in the field difficult. 



As a fitting close to these observations on the distribution of 

 lichens in different regions of the state I may give some notes 

 concerning certain species for most part characteristic of more 

 southern portions and found also in northeastern Minnesota. 

 Parmelia borreri Turn, was not found fruited along the lake 

 north of Beaver Bay. Peltigera aphlhosa (L.) Hoffm. seeks 

 high ground in the southern stations from which it is recorded 

 and in the northwestern as well and is one of the species whose 

 farther southern and western extent in the state would be espe- 

 cially worthy of study. Parmelia tiliacea (Hoffm.) Tuck, be- 



