156. Evernia] 40. USNEACEAE 339 



on deflexed tips, the disk flat to convex, dark chestnut-brown, the exciple entire 

 to toothed ; spores ellipsoid, 7-1 1 X 5-6 /x. 

 On rocks, in alpine regions, Oregon. 



40. USNEACEAE 



Thallus fruticose, erect or hanging, usually radial, rarely dorsiventral, differen- 

 tiated into a cortical layer, surrounding a thin algal layer and the central hollow 

 or solid medullary cylinder, attached to the substratum by rhizoids; apothecia 

 round, sessile or somewhat pedicellate, with a thalloid exciple. 



The algal host is Protococcus. 



A. Spores non-septate 

 B. Apothecia frequent 



C. Thallus dorsiventral 156. Evernia 



C. Thallus upright or hanging 



D. Thallus short 157. Dufourea 



D. Thallus much elongated 



E. Thallus greenish gray or straw-colored 160. Usnea 



E. Thallus brownish to brown 158. Alectoria 



B. Apothecia unknown 



C. Podetia with hollow centers 161. Thamnolia 



C. Podetia solid 162. Siphuxa 



A. Spores 1-3-septate 159. Ramalina 



156. Evernia Ach., Lich. Univ. 84. pi. 10, f. 1-3. 1810. 



Thallus fruticose, erect to prostrate, or hanging, much branched, often en- 

 tangled, differentiated into a thin irregular pseudo-cortex, an algal layer of large 

 cells, and the medullary layer composed of loosely interwoven hyphae usually sur- 

 rounding a more or less complete hollow cylinder; apothecia large, terminal or 

 marginal, the disk concave, differing in color from the thallus, the margin colored 

 like the thallus, persistent; hypothecium hyaline; hymenium hyaline to brownish 

 below, brownish above; paraphyses thick, unbranched; asci short; spores 8, hyaline, 

 non-septate, commonly ellipsoid. 



The algal host is Protococcus. 



A. Thallus more or less sorediate 3. E. prunastri 



A. Thallus not sorediate 



B. Thallus straw-colored or greenish to sulphur-colored 



C. Thallus straw-colored, branches beset with prickles ... 2. E. divaricata 



C. Thallus sulphur-colored, obscurely pitted 1. E. vulpina 



B. Thallus greenish gray to ashy 



C. Thallus usually bearing scales or coralloid branchlets above . 4. E. furfuracea 

 C. Thallus without scales or coralloid branchlets 



D. Branches smooth, very slender 5. E. ceratea Cladonia 



D. Branches wrinkled above 5. E. ceratea 



1. Evernia vulpina (L.) Ach., Lich. Univ. 443. 1810. 



Lichen vulpinus L., Sp. PI. 1155. 1753. Letharia vulpina (L.) Hue. E. vulpina 

 var. calijornica (Lev.) Mull. Arg. 



Thallus tufted or rarely pendulous, rigid, greenish to sulphur-colored, sub- 

 cylindrical to flattened, and angular, wrinkled, obscurely pitted, frequently ex- 

 panded toward the base, dichotomously much-branched, the branches strongly 

 diverging, the tips tapering; apothecia large, 3-20 mm. across, subterminal, the 

 disk concave, the exciple wrinkled, sometimes radiately extended above into 

 narrow branches and usually bearing one or more larger branches below; spores 

 short-ellipsoid, 5-8.5 X 4.5-5.5 fx. 



On trees and old wood, rarely on rocks, from Nebraska and South Dakota 

 westward to the Pacific Coast. 



