172 MINNESOTA BOTANICAL STUDIES. 



Avoiding unnecessary detailed statement, it may be briefly 

 stated that the present list adds 64 lichen species and varieties to 

 the flora of the state, and with about 20 Minnesota lichens yet 

 undetermined, brings the whole number of lichens for the state 

 very near to the 500 mark set by the State Botanist a few years 

 ago.* The estimate seemed high at the time, but a month's 

 search for new species in northern Minnesota would pass it con- 

 siderably ; and it is now safe to increase the estimate to 700, a 

 number which may not be reached, though there is little doubt 

 that many lichen forms exist in the state. Of the 64 one is new, 

 and 13 more are new to North America. Besides these, several 

 are not yet determined. The northern portion of the state has 

 now been studied more than parts farther south, but this part of 

 Minnesota is by far the most interesting to the lichenist and 

 would surely still yield more new material than most areas far- 

 ther south in the state. 



All of the northern boundary has been studied more or less, 

 except the region in the Red river valley, which is very poor in 

 lichens ; and as other features of origin and distribution were 

 considered in the work to the eastward of the present area in 

 1897, it is the more fitting that the formations should receive 

 special attention in this paper. The two areas are somewhat 

 similar as to lichen floras, and the two papers will thus supple- 

 ment each other, the present bringing out features which con- 

 stantly obtruded themselves in 1897, but which could not re- 

 ceive attention. 



Before passing to the lichen societies of the region, some 

 general statement as to substrata will be in order. No lime- 

 stones were seen during the summer, all of the rocks being 

 those of the Archaean or Algonkian groups. To the westward 

 cedar and tamarack swamps abounded, especially the former. 

 Hard-wood trees were found here, but they are not numerous, 

 and attention was given largely to the swamps, which furnish 

 the most interesting field in Minnesota for the lichenist. Pass- 

 ing eastward and southward fewer and smaller swamps were 

 found, and more rock exposures. A great variety of substrata 

 was investigated, as will appear in passing in order the large 

 number of formations to follow. A matter of special interest 

 was the opportunity offered of studying further the swamp for- 

 mations previously investigated farther south. Also, time was 



*MacMillan, C. Minnesota Plant Life, 95. 1899. 



