USNEA. | USNEEI. 201 
Tribe X. USNEET Nyl. Mém. Soc. Cherb. iii. (1855) p. 170. 
Thallus fruticulose, somewhat rounded, rarely angulose, erect or 
pendulous, internally with a firm chondroid axis. Apothecia leca- 
norine, peltate, terminal or lateral; spores Snz, small, simple, 
colourless ; paraphyses not discrete. Spermogones immersed ; sterig- 
mata simple or subsimple. 
A natural tribe, distinguished from its allies by having internally a 
solid axis (as in Stereocaulon), which readily separates from the cortical 
layer. Comprising only three small genera, two of which, Newropoyon 
and Chlorea, do not occur in Great Britain, it is with us, as in most other 
countries, marked by the abundance of the species of Usnea. 
37. USNEA Dill. Muse. (1741) p. 56 pro parte; Ach. Meth. 
(1803) p. 306.—Thallus filamentoso-elongate, or tibrilloso-ramulose 
with patent branches, concolorous on both sides; chondroid axis 
composed of densely conglutinate filaments, cortical layer fragile 
and often diffract. Apothecia concolorous or subconcolorous with 
Fig. 40. 
Usnea florida Ach.—a. Longitudinal section of the thallus, x200. 2. Vertical 
section of a young apothecium (with thalline receptacle), x30. ¢. Theca and 
paraphysis, X350. d. Spores, 500. ¢. Transverse section of the thallus, 
showing above a spermogoné (beneath which is a section of the medulla), 
x30. f. Sterigmata and spermatia, x 500. 
the thallus, often with ramuloso-ciliate margin; hypothecium colour- 
less ; spores small, ellipsoid; paraphyses _ stipate in the dense 
hymenial gelatine, which is bluish with iodine. Spermogones 
lateral, slightly protuberant, in colourless conceptacles ; spermatia 
straight, cylindrico-acicular, slightly incrassate towards the base. 
