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 Verrucaria 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 Cladonia-Pclligera 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 

 Cladonias, which nourish 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 



(BEMIDJI). 



Peltigera horizontalis (L.) HOFFM. 



Peltigera canina (L.) HOFFM., C. 



Peltigera canina (L.) HOFFM. var. spuria ACH. 



Peltigera canina (L.) HOFFM. var. sorediata SCHAER., C. 



Collema pulposum (BERNH.) NYL., C. 



Collema limosum ACH. 



Collema crispum BORR. 



Cladonia cariosa (Acn.) SPRENG. 



Cladonia pyxidata (L.) FR., C. 



Cladonia degenerans FLK. 



Cladonia gracilis (L.) NYL., C. 



Cladonia gracilis (L.) NYL. var. symphycarpia TUCK. 



Cladonia gracilis (L.) NYL. var. verticillata FR., C. 



Cladonia gracilis (L.) NYL. var. elongata FR. 



Cladonia gracilis (L.) NYL. var. hybrida SCHAER. 



Cladonia cornuta (L.) FR. 



Cladonia furcata (Huos.) FR. 



Cladonia rangiferina (L.) HOFFM. 



Cladonia rangiferina (L.) HOFFM. var. alpestris L. 



Cladonia uncialis (L.) FR. 



*Fiuk, B. 1. c., 294-295. 



