298 MINNESOTA BOTANICAL STUDIES. 



less numerous. All the species of these formations, except the 

 Biatoras, .have been found elsewhere in Minnesota, but not ag- 

 gregated into definite formations. 



Comparing the last two series of formations, viz., those of 

 calcareous earth and those of drift pebbles of the same areas, 

 it will be noted that the former, because of their position on 

 dry hill-sides, consist as a whole of lichens having small foli- 

 aceous or granular thalli, while those on the yet dryer and 

 harder calcareous pebbles are almost entirely made up of strictly 

 crustaceous plants. 



The formations of exposed and shaded limestone bluffs come 

 next in natural order, and the analysis is difficult, since some of 

 the lichens of these formations grow about equally well in sun- 

 shine and shade. These 1 shall indicate by an interrogation 

 point (?). From the prevalence of gelatinous lichens they may 

 be named as follows : 



Gelatinous lichen formation of shaded (or damp) limestone 

 bluffs (Mankato). 



Pannaria nigra (HUDS.) NYL. 



Pannaria languinosa (Acn.) KOERB. 



Omphalaria kansana TUCK. ? 



Omphalaiia pulvinata NYL. ? 



Collema plicatile SCHAER. 



Collema pustulatum ACH. 



Leptogium lacerum (Sw.) FR. 



Placodium citrinum (HOFFM.) LEIGHT. 



Biatora inundata FR. 



Buellia alboatra (HOFFM.) TH. FR. var. saxicola FR. 



Endocarpon miniatum (L.) SCHAER. 



Staurothele umbrina (\VAHL.) TUCK. 



Similar formations do not exist in other surveyed portions of 

 Minnesota, except at Minneapolis, where the development is 

 poor. It is as follows : 



Gelatinous lichen formation of shaded (or damp] calcareous 

 rocks (Minneapolis). 



Pannaria nigra (HUDS.) NYL., C. 

 Pannaria languinosa (Acn.) KOERB., C. 



