160. Usnea] 40. USNEACEAE 349 



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160. Usnea (Dill.) Adans., Fam. PI. 2:7. 1763. 



Thallus fruticose, erect or pendulous, commonly branched, cylindrical or some- 

 times angular, smooth to more or less rough, differentiated into a cortical layer 

 of closely interwoven, variously extending hyphae, a thin algal layer, and medullary 

 tissue composed of a central cylinder of closely interwoven, longitudinally extending 

 hyphae and a surrounding cylinder of loosely interwoven hyphae, uniting the inner 

 portion of the medullary tissue and the cortex; apothecia small to large, lateral or 

 terminal, sessile, the disk cyathiform to slightly concave, greenish to flesh-colored or 

 buff, the exciple colored like the thallus, more or less irregular; hypothecium hya- 

 line; hymenium hyaline; paraphyses agglutinate, more or less branched; asci 

 clavate to cylindrico-clavate; spores 8, hyaline, ellipsoid or round-ellipsoid, non- 

 septate. 



The algal host is Protococcus. 



A. Thallus papillate 



B. Thallus rigid, erect 



C. Thallus very rigid, fibrinoid branchlets stiff .... 1. U. florida strigosa 



C. Thallus not so rigid, fibrilloid branches flexible 1. U. florida 



B. Thallus flexible, pendant 



C. Branches slender, sparingly divided, fibrilloid 



branchlets rarely divided 3. U. barbata 



C. Branches coarser, much divided, fibrilloid branches 



frequently divided 2. U. plicata 



A. Thallus not papillate 



B. Branches coarse, angulate 4. U. angulata 



B. Branches slender, not angulate 



C. Thallus scaly whitish-sorediate 6. U. longissima 



C. Thallus smooth 



D. Thallus usually pitted near the base 5. U. cavernosa 



D. Thallus not pitted 7. U. trichodea 



1. Usnea florida (L.) Web., in Wigg., Prim. Fl. Hols. 91. 1780. 



Lichen floridus L., Sp. PI. 1156. 1753. U. florida f. major Michx. U. mutabihs 

 Stirt. U. barbata var. florida f. rubiginea (Michx.) Tuck. U. barbata var. 

 hirta (L.) E. Fries. U. barbata var. comosa (Ach.) Biroli. 



Thallus small, erect, rigid, tufted, shrublike, greenish gray, rarely reddening or 

 blackening, sometimes sorediate, soon rough and more or less papillate, the cortex 

 frequently seamed or broken in partial or complete rings, sometimes exposing the 

 whitish medulla within, the branches coarse, cylindrical, short, spreading, much di- 

 vided, usually dichotomously, bearing numerous, short, rectangularly divergent, rare- 

 ly divided, fibrilloid branchlets; apothecia small to large, 2-12 mm. across, or larger, 

 terminal, the exciple frequently lobate or torn, radiately extending into fibrilloid 

 branches; spores 6-10 X 4-8 ft. (Plate 42 a.) 



On trees, old wood, and rarely on rocks, throughout the United States. 



var. strigosa Ach., Meth. Lich. 310. 1803. 

 Thallus very rigid, the branches short, bearing numerous short, stiff, sharp- 

 pointed fibrilloid branchlets; apothecia large, the disk greenish. 



On trees and old wood, from Maine to Iowa, and southward to New Mexico. 



2. Usnea plicata (L.) Wigg., Prim. Fl. Hols. 91. 1780. 



Lichen plicatus L., Sp. PI. 1154. 1753. U. barbata var. plicata (L.) E. Fries. 

 U. linearis Schneid. U. plicata var. Htiei (Boist.) Howe. U. barbata var. 

 ceratina (Ach.) Schaer. U. calij ornica Herre. 



Thallus pendulous, flexible, greenish gray to straw-colored, rarely reddening, 

 sometimes sorediate, usually rough, thickly papillate, especially toward the base, 

 the cortex often seamed or broken in partial or complete rings, sometimes exposing 

 the whitish medulla within, the branches coarse, long, cylindrical, lax or frequently 

 interwoven, rather spreading, much divided, usually dichotomously, frequently 

 bearing scattered, rectangularly divergent, frequently branched, fibrilloid branch- 

 lets; apothecia middle-sized to large, 3-10 mm. across, lateral or subterminal, the 



