Fink : LICHENS OF THE MINNESOTA VALLEY. 305 



The two formed on smooth bark at Granite Falls and not at 

 Mankato are Lecidea cntcroleuca Fr. var. achrista Schaer. and 

 Arthonia punctiforniis Ach. As in the rough bark formations, 

 the one at Mankato is richer for the same reason and, strangely 

 enough, my study of the Granite Falls area only discovered a 

 single Pyrcnula on smooth bark. My name is scarcely appro- 

 priate for this formation, though it is for the one at Mankato as 

 it would be for others from other localities in Minnesota and 

 Iowa which might be added. Without adding another list or 

 another complete formation, I have indicated by (F) in the 

 above list the Pyrenulas of that list which occur on smooth 

 bark at Fayette, Iowa. 



Persons acquainted with lichen species will readily observe 

 in the lists for rough bark and smooth bark lichen formations, 

 that the formation on rough bark is composed principally of the 

 more foliaceous and fruticulose lichens while those of the smooth 

 bark formations are in the main crustaceous lichens. This is 

 possibly due in part to the fact that these foliaceous and fruti- 

 culose lichens more easily gain a foothold on the rough bark 

 which breaks up the thallus of the lichens adapted to smooth 

 bark, thus tending to kill them. However it is probable that 

 light, shade and moisture are also factors, the large trees fur- 

 nishing more shade than the smaller ones. 



Next in order naturally enough we may consider the lichen 

 formations of old boards and old wood, and the formations are 

 so nearly alike for Mankato and Granite Falls that they may be 

 treated in a single list by giving the Mankato list and marking 

 (G) those common to the Granite Falls formation also. Our 

 Calicei are lichens seldom seen in any other formations, hence 

 the following name may be applied. 



Calicei lichen formation of old boards and wood 

 (Mankato). 



'heloschistes chrysopthalmus (L.) NORM., G. 



lacodium cerinum (HEDW). NAEG. and HEPP. var. pyrocea 

 NYL., G. 



Lecanora hageni ACH., G. 



Lecanora varia (EHRH.) NYL., G. 



Rinodina sophodes (AcH.) NYL., G. 



Rinodina sophodes (Acn.) NYL., var. exigua FR., G. 



