292 MINNESOTA BOTANICAL STUDIES. 



third division, consisting of two Peltigeras, scarcely needs any 

 special consideration. 



I shall next consider the similar shaded rock formation at 

 New Ulm, which may be divided into those lichens naturally 

 belonging to the rocks and those probably migrating from trees. 



Mixed lichen formation of shaded rocks (New Ulm). 



A. Naturally belonging to the rocks. 

 Pannaria languinosa (Ach.) Koerb. 

 Collema flaccidum Ach. 



Collema furvum (Ach.) Nyl. 



B. Near trees and probably migrated from them. 

 Theloschistes lychneus (Nyl.) Tuck., CTS. 

 Parmelia crinita Ach., CTS. 



Parmelia borreri Turn., CTS. 

 Parmelia saxatilis (L.) Fr., CTS. 



Parmelia saxatilis (L.) Fr. var. panniformis (Ach.) Schaer., 

 C. 



Parmelia caperata (L.) Ach., CTS. 

 Physcia speciosa (Wulf. Ach.) Nyl., CTS. 

 Physcia pulverulenta(ScHREB.) Nyl., CTS. 

 Physcia stellaris (L.) Tuck., TS. 

 Physcia obscura (Ehrii.) Nyl., CTS. 



As to the shaded rock lichen formations of the region sur- 

 veyed considering only plants naturally belonging to the rocks, 

 there is not a single lichen that is common to all of them. Pan- 

 naria languinosa (Ach.) Koerb. is the most constant element 

 of such formations, which as a whole might be named for this 

 plant were it not quite as common in shaded limestone forma- 

 tions otherwise quite different from any of those on the rocks 

 under consideration at present. Of the lichens of the shaded 

 rock formation at New Ulm, which have probably migrated 

 from trees, the nine marked common (C), may be taken as the 

 ones most commonly occurring, as they were found also at 

 Granite Falls in the similar formation. Those marked (T) all 

 but one of the nine, occur in the similar formation at Taylors 

 Falls. Other elements vary more with change in various eco- 

 logic factors. The similar partial formation was noted at 

 Grand Portage, especially on the island, and adding those 



