350 40. USNEACEAE [ 160. Usnea 



l 



exciple entire or radiately extending into fibrinoid branchlets; spores 6-10 X 4-8 /x. 

 On trees and sometimes on old wood, throughout northern United States, and 

 southward to the Gulf of Mexico, and in California. 



3. Usnea barbata (L.) Wigg., Prim. Fl. Hols. 91. 1780. 



Lichen barbatus L., Sp. PI. 1155. 1753. U. barbata var. dasypoga Ach. U. phcata 

 var. barbata (L.) E. Fries. U. barbata var. pendula (Schaer.) Krempl. 



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

 often blackening toward the base, sometimes bursting-sorediate, rough, more or less 

 papillate, especially toward the base, the cortex sometimes seamed or broken in 

 partial or complete rings, and rarely exposing the whitish medulla within, the 

 branches rather slender, long, cylindrical, spreading, sparingly divided, usually 

 dichotomously, rarely finally interwoven, bearing numerous, rather short, rectangu- 

 larly divergent, rarely divided, fibrilloid branchlets; apothecia small, 1.5-6 mm. 

 across, rare, lateral or subterminal, the exciple entire or radiately extending into 

 fibrilloid branchlets; spores 6-10X4-8 /a. 



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



4. Usnea angulata Ach., Syn. Lich. 307. 1814. 



Thallus pendulous, rigid, greenish gray to straw-colored, finally darkening, 

 rough, frequently scaly, the branches coarse, angulate, often very long, sparingly 

 divided dichotomously, bearing numerous, slender, sometimes branched, fibrilloid 

 branchlets; apothecia middle-sized to large, 5-1 5 mm. across, lateral, terminal, or 

 subterminal, the exciple smooth or netted-veined, usually extending into fibrilloid 

 branchlets; spores 5-9X4-6//. 



On trees, throughout northern United States. 



5. Usnea cavernosa Tuck., in Agassiz, Lake Superior 171. 1850. 



Thallus pendulous, flexible, greenish gray, the cortex sometimes seamed and 

 ridged or broken in partial or complete rings, rarely exposing the whitish medulla 

 within, the branches slender, cylindrical or subcylindrical, long, rough, especially 

 toward the base, and pitted, much-divided dichotomously, bearing long, slender, 

 twisting, more or less scattered, fibrilloid branchlets; apothecia small, 1-4.5 mm. 

 across, lateral, the exciple usually extending into rather numerous fibrilloid branch- 

 lets; spores 6-9 X 4-6.5 /x. 



On trees, Maine, New Hampshire, Michigan, Iowa, Minnesota, South Dakota, 

 Colorado, Arizona, and Washington. 



6. Usnea longissima Ach., Lich. Univ. 626. 1810. 



Thallus pendulous, flexible, greenish gray to straw-colored, the branches slender, 

 often very long, subcylindrical or flattened, sparingly divided, rough, scaly whitish- 

 sorediate, especially toward the base, bearing numerous, rather straight, rectangu- 

 larly divergent, often long, rarely divided, fibrilloid branchlets; apothecia small, 

 1-3 mm. across, very rare, terminal, the exciple usually extending into fibrilloid 

 branchlets; spores 7-10 X 4-6 ft. 



On trees and sometimes on old wood, throughout northern United States. 



7. Usnea trichodea Ach., Meth. Lich. 312. 1803. 



U. trichodea var. ciliata Mull. Arg. 



Thallus pendulous, flexible, greenish gray, sometimes bursting-sorediate, smooth, 

 or rough toward the base, often seamed and ridged or broken in partial or com- 

 plete rings, sometimes exposing the whitish medulla within, the branches slender, 

 long, cylindrical, much divided, usually dichotomously, bearing long, slender, twist- 

 ing, fibrilloid branchlets; apothecia small, 1.5-4 mm. across, lateral, the exciple 

 entire or extending into scattered fibrilloid branchlets; spores 6-10 X 4-8 /x. 



On trees, usually conifers, and old wood, from New England to Alabama, and 

 westward to Texas and Minnesota. 



OTHER SPECIES REPORTED 

 Usnea articulata (L.) Hoffm. — Minnesota and the Pacific Coast. 



