176 LICHENS OF THE STATE OF WASHINGTON 



A, Thallus definitely brown or more rarely grayish brown... 5. P. muscigena 

 A. Thallus never brown or grayish brown. 

 B. Thallus sorediate. 



C. Soredia on margins of thallus. 



D. Lower surface of thallus dark brown or black, upper cortex 



shows no color change with KOH. 4. P. leucoleiptes 



D. Lower surface of thallus white or light buff, upper cortex 



yellow with KOH. 8. P. tribacia 



C. Soredia scattered over surface of thallus, upper cortex yellow 



with KOH 2. P. caesia 



C. Soredia on the under surface of inflated vaulted tips, upper cortex 



shows no color change with KOH 3. P. hispida 



B. Thallus never sorediate. 



E. Thallus pruinose, always light colored, margins of lobes prostrate. 



6. P. pulverulenta 

 E. Thallus not pruinose. 



F. Lower surface of thallus white, with concolorous rhizoids. 



7. P. stellaris 

 F. Lower surface of thallus brown or black, with concolorous 



rhizoids 1. P. aipolia 



1. Physcia aipolia (Ehrh.) Hampe in Fiirnr. Nat. Topogr. Regensburg, 



2:249. 1839. 

 Lichen aipolius Ehrh. in Humb. Fl. Friburg. Specim. 19. 1793. 

 Physcia stellaris var. aipolia (Ehrh.) Hampe. 



Thallus pale grayish-green or drab (R), foliose, circular, expanded, 

 appressed, lobes much divided, narrow elongated, sinuous, imbricated, mar- 

 gins entire or crenate; below brown or black, with concolorous rhizoids. 

 Apothecia 0.5-1.5 mm. in diameter, sessile ; disk dark brown or black, white 

 pruinose, concave to slightly convex, thalline margin thick, prominent con- 

 colorous with the thallus, somewhat crenate ; hypothecium hyaline ; spores 

 brown, ellipsoid, 1 -septate, 16.8-25.0 x 6.9-11.0 /x. Cortex and medulla 

 yellow with KOH. 



On trees and rocks : Yakima Co. : American River Camp, 2800 ft., 

 1931, 949. Clallam Co.: Elwha River, near Port Angeles, 1940, 2930. 

 Clallam Co.: Dungeness, 1913, Foster 2543 (F). 



2. Physcia caesia (Hofifm.) Hampe in Fiirnr. Nat. Topogr. Regensburg, 



2:250. 1839. 

 Lichen caesius Hofifm. Enum. Lich. 65. 1788. 



Thallus pale greenish gray or ivory yellow (R), foliose, circular, adnate, 

 lobes branched, narrow elongated, somewhat imbricated, bearing circular 

 spots of gray soredia, margins entire or crenate ; below pale or rarely 

 black, with black rhizoids. Apothecia 0.5-2.0 mm. in diameter, sessile ; disk 

 dark brown or black, often gray pruinose, slightly concave to flat ; thalline 

 margin infiexed, entire or crenulate ; hypothecium hyaline ; spores brown, 

 ellipsoid, 1-septate, 19.8-22.0 x 6.6-12.0 fx. Cortex yellow with KOH. 



