130 CUMMINGS 



having seen a specimen in the Kew Herbarium which was collected by 

 Parry and labeled as from the ' North Pole.' Dr. Arnold makes no 

 mention of its occurrence in Newfoundland or Labrador in his lists of 

 the lichens of those regions. Neither of the St. Paul specimens shows 

 apothecia, and both are only slightly pulverulent. They may possibly 

 be referred to P. muscigena of Fries' Lichenes Arctoi. 



Additional Alaska species : P. obscura (Ehrnb.) Nyl., listed by 

 Rothrock as having been collected at Kotzebue Sound ; P. obscura 

 sciastra (Ach.) Nyl., and P. muscigena (Wahl.) Nyl., both 

 recorded by Nylander as occurring at Port Clarence ; and P. melops 

 ossicola Nyl., collected on St. Lawrence Island, as recorded by Ny- 

 lander. 



PARMELIA. 



KEY TO THE SPECIES. 



Thallus straw-colored. 



Thallus large, of ten isidiophorous, lobes variously divided., conspersa. 



Thallus small, sorediate, dichotomously divided ambigua. 



Thallus variously colored. 

 Thallus olivaceous brown. 



Lobes of thallus flat, rounded crenate olivacea. 



Lobes of thallus linear or terete. 



Palmately divided , stygia. 



Dichotomously divided lanata. 



Thallus glaucescent or blackening. 



Thallus small, dichotomously divided, sorediate. 



ambigua albescens. 

 Thallus large, not dichotomously divided. 



Thallus gray, sometimes with blackening borders. 

 Thallus more or less reticulate, not inflated. 



Thallus whitish, sorediate saxatilis. 



Thallus grayish, not sorediate saxatilis sulcata. 



Thallus not reticulate, inflated. 



Lobes of thallus wide and much inflated, not black-mar- 

 gined physodes enteromorpha. 



Lobes of thallus narrow, somewhat inflated. 



Lobes of thallus not black-margined physodes. 



Lobes of thallus black-margined .physodes vittata. 



Thallus blackening all over. 



Lobes of thallus flat, broad, not inflated. 



saxatilis omphalodes. 

 Lobes of thallus rounded, narrow, inflated. 



physodes obscurata. 



