Fink: LICHENS OF NORTHWESTERN MINNESOTA. 667 
more loosely attached by rhizoids. However, those undoubtedly 
belonging to the rocks have poorly developed thalli with no 
cortex or an upper pseudo-cortex, and Verrucarta muralis Ach., 
an intruder usually growing upon calcareous rocks in exposed 
places, is essentially hypolithic. That the three forms having 
poorly developed and epilithic thalli should seek ombrophytic 
associations is, of course, natural enough. 
The Cladonza-Peltigera formation of shaded earth was found 
remarkably well developed under the pines at Bemidji. The 
table of species below shows 20 forms. The formation here, 
though containing the same genera as the similar one farther 
south,* is twice as well developed, being especially rich in 
Cladonzas, which flourish under the pines. I have marked (C) 
the five species common to the similar formations noted for the 
state, as being the most constant elements of such formations, 
at least in Minnesota. I shall now record the formation and 
follow with a discussion of structure of the lichens composing it. 
CLADONIA-PELTIGERA LICHEN FORMATION OF SHADED EARTH 
(BEMIDJI1). 
Peltigera horizontalis (L.) Horr. 
Peltigera canina (L.) Horrn., C. 
Peltigera canina (L.) Horrm. var. spuria Acu. 
Peltigera canina (L.) Horr. var. sorediata ScHAER., C. 
Collema pulposum (BEerRNu.) Nyt., C. 
Collema limosum Acu. 
Collema crispum Borr. 
Cladonia cariosa (AcH.) SPRENG. 
Cladonia pyxidata (L.) Fr., C. 
Cladonia degenerans FLK. 
Cladonia gracilis (L.) Nyt., C. 
Cladonia gracilis (L.) Nyx. var. symphycarpia Tuck. 
Cladonia gracilis (L.) Ny. var. verticillata Fr., C. 
Cladonia gracilis (L.) Ny. var. elongata FR. 
Cladonia gracilis (L.) Nyu. var. hybrida Scuarr. 
Cladonia cornuta (L.) Fr. 
Cladonia furcata (Hups.) FR. 
Cladonia rangiferina (L.) Horrn. 
Cladonia rangiferina (L.) Horr. var. alpestris L. 
Cladonia uncialis (L.) Fr. 
*Fink, B. 1. c., 294-295. 
