668 MINNESOTA BOTANICAL STUDIES. 
Comparing the lichens of this formation with those of the 
shaded rock formation above, we find that, as a result_of the 
more moist habitat of the forms, growing on earth in shade and 
usually on an abundance of decaying vegetable remains which 
hold moisture, the formation consists of plant individuals even 
less closely attached to the substratum, except perhaps the 
Collemas, which have no cortex and which, therefore, even in 
their shaded situation, remain close to the substratum to absorb 
the moisture which is rapidly evaporated from their non-cellular 
surfaces. The Peltigeras with a well developed upper cortex 
hold moisture better and rise somewhat higher. The podetia of 
the Cladonzas have a surrounding pseudo-cortex of densely 
interwoven hyphe, which serves for protection against too 
rapid evaporation of moisture as well as for mechanical sup- 
port. Hence the Cladonzas rise vertically and are especially 
numerous as to species and individuals in this moist and shaded 
formation, as well as unusually luxuriant. Thus it appears 
that we have in this formation, as in those already considered 
plants adapted in very different ways to the environment. 
The remarkable constancy of occurrence of certain floral 
elements in certain environments can scarcely be better illus- 
trated than by comparing the calcareous earth lichen formation 
given below with similar ones recorded in the fifth paper of this 
series for Granite Falls, Minnesota, and Fayette, Iowa.* 
BIATORA DECIPIENS LICHEN FORMATION OF EXPOSED CALCA- 
REOUS EARTH (LEAF HILLS). 
Heppia despreauxii (Mont.) Tuck., C. 
Urceolaria scruposa (L.) Nyt., C. 
Biatora decipiens (EurRH.) FR., C. 
Biatora decipiens (Euru.) Fr. var. delabata Auct., C. 
Biatora muscorum (Sw.) Tuck., C. 
Endocarpon hepaticum Acu., C. 
All of the six floral elements recorded in the present forma- 
tion and marked (C) are also listed in the formation at Granite 
Falls and Fayette, and each of these last two contains a single 
rare species not discovered in the Leaf hills formation. As in 
the localities previously studied, the formation in the hills is best 
developed on the hill-sides where the plants are washed with 
the lime-impregnated water which flows down the slope during 
* Fink, B. l. c., 295-296. 
