300 MINNESOTA BOTANICAL STUDIES. 



ever the bluffs exist. With the greater amount of moisture at 

 the water's edge, some of the plants of the Fayette formation 

 grow well in sunshine and even on south exposures. These I 

 have indicated by an interrogation point (?). These, for most 

 part gelatinous lichens, require a good amount of moisture ; and 

 if growing far from water seek shade for it. In the Fayette 

 locality many trees have been cut recently along the bluffs so 

 that the plants are more exposed than formerly. The Minne- 

 apolis list can be considered a formation only in the sense of a 

 group of plants growing under like conditions, for owing to 

 somewhat dryer climate the formation is poorly developed as to 

 individuals and may be designated as a scattered formation, 

 only one or two of the species usually growing in one limited 

 area, along the bluffs and long stretches of bluff between these 

 areas frequently not bearing a single plant of the formation. 



Next in order comes the lichen formation of exposed lime- 

 stone bluffs, which I shall designate as follows from the presence 

 of a large proportion of angiocarpous lichens. 



Angiocarpous lichen formation of limestone bluffs (Mankato). 



Theloschistes lychneus (NYL.) TUCK. 

 Placodium elegans (LINK.) DC. 



Placodium vitellinum (EHRH.) NAEG. and HEPP var. aurel- 

 lum ACH. 



Placodium aurantiacum (LIGHT.) NAEG. and HEPP. 

 Lecanora hageni ACH. 

 Lecanora erysibe NYL. ? 

 Endocarpon pusillum HEDW. ? 

 Endocarpon miniatum (L.) SCHAER. ? 

 Staurothele diffractella (NYL.) TUCK. 

 Verrucaria fuscella FR. 

 Verrucaria nigrescens PERS. 

 Verrucaria muralis ACH. 



I might add similar formations from Minneapolis and Fayette, 

 Iowa ; but the analysis is very uncertain so that the comparisons 

 could have little value. 



I shall now consider the sandstone bluff formations of certain 

 localities, simply designating them as formations of damp sand- 

 stone since they are found along streams where the rocks are 



