302 MINNESOTA BOTANICAL STUDIES. 



Comparing the two formations we find six common lichens of 

 a total of nine recorded for the first and eleven for the second. 

 Similar formations occur at Pictured Rocks, Iowa, and at Rap- 

 idan, but I shall not multiply lists. As in the instance of cer- 

 tain formations on shaded granite or quartzite recorded above, 

 both of these formations are more or less mixed, being made 

 up of lichens strictly lithophytic in adaptation and of others 

 which have doubtless wandered from trees or from earth. As 

 I have not been able to study such sandstone bluffs at a distance 

 from trees, I have not attempted a definite analysis of these 

 more limited formations as I did for the formations of the shaded 

 granite and quartzite, but have simply indicated in the second 

 list those which have probabl}^ wandered from trees by (T) and 

 those from earth by (E). I have omitted from these sandstone 

 formations some of the rarer plants which I should have in- 

 cluded had I attempted an analysis of these mixed formations. 



I shall now proceed to the two formations of trees, viz., that 

 of rough barked trees and that of trees having smooth bark. 

 The distinctions are difficult in some instances as certain species 

 grow in both habitats. Consequently, as in some instances, in 

 formations previousl}^ considered, some plants are recorded for 

 more than one formation. Moreover, it must be added that 

 some of those recorded for rough barked trees frequently seek 

 the smoother portions of the bark. The subfamily Parmelei is 

 especially well developed in the rough bark formations, which 

 may accordingly be named as follows : 



Parmelei lichen fo7'mation of trees zvith rough bark (Mankato). 

 Ramalina calicaris (L.) Fr. var. fraxinea Fr., G. 

 Ramalina calicaris (L.) Fr. var. fastigiata Fr., G. 

 Theloschistes chrysopthalmus (L.) Norm., G. 

 Theloschistes polycarpus (Ehrh.) Tuck., G. 

 Theloschistes lychneus (Nyl.) Tuck., G. 

 Theloschistes concolor (Dick.) Tuck., G. 

 Parmelia perforata (Jack.) Ach. 

 Parmelia crinita Ach., G. 

 Parmelia borreri Turn., G. 

 Parmelia tiliacea (Hoffm.) Floerk., G. 

 Parmelia saxatilis (L.) Fr. 

 Parmelia caperata (L.) Ach., G. 



