672 MINNESOTA BOTANICAL STUDIES. 



Lecanora subfusca (L.) ACH. 



Lecanora varia (EHRH.) NYL. 



Rinodina sophodes (Acn.) NYL. 



Biatora atropurpurea (MASS.) HEPP. 



Biatora rubella (EHRH.) RABENH. 



Lecidea enteroleuca FR. 



Buellia parasema (Acn.) TH. FR. 



Graphis scripta (L.) ACH. 



Arthonia lecideella NYL. 



Arthonia radiata (PERS.) TH. FR. 



Sagedia oxyspora (NYL.) TUCK. 



Pyrenula punctiformis (Acn.) NAEG. var. follax NYL. 



Pyrenula cinerella (FLOT.) TUCK. var. quadriloculata FINK. 



Pyrenula leucoplaca (WAHL.) KBR. 



Pyrenula leucoplaca (WAHL.) KBR. var. pluriloculata var. 

 nov. 



Inspection of the list of plants given above for the rough 

 bark formations based on characters of substratum, shows 

 lichens varying widely structurally and adapted to the forma- 

 tion in very different ways. There are the Biatoras, which 

 usually occur in the more moist and shaded spots in this 

 scattered formation and have small thalli usually without cellu- 

 lar cortex. The same may be said of the Buellias and the 

 Acolium, while the Lecanoras, Placodzums, and Pertusarias 

 usually have somewhat larger thalli and some indication of an 

 upper cortex at least. Even more rudimentary than any of the 

 above are the thalli of the Opegraphas, Graphics, Pyrenulas 

 and the Coniocybe which are hypophloeodal and thus protected. 

 However the Collemas without cellular cortex rise to the foli- 

 aceous type, but seek very damp and well shaded habitats. 

 The Leptogium^ with upper cortex only, seeks damp places 

 also. Next may be considered the Theloschistes, Parmelias 

 and Physcias with foliaceous thalli having good cortex on all 

 sides, and which are not so closely adnate to the substratum as 

 the crustaceous forms. Finally we have the fruticulose type of 

 structure represented in the formation in the Ramalinas and 

 Usneas. These plants have a good cortex on all sides though 

 not cellular at least in the first genus, and in well shaded and 

 moist portions of the formation are quite common. This for- 

 mation furnishes the most variety as to methods of adaptation 

 of any herein recorded. 



