USNEA.] 



201 



Tiil)c X. US NE E I Xyl. Mem. Soc. Cherb. iii.ClSoo) p. 170. 



TluiUus I'niticiiloso, soracwhiit rouiulotl, rarely an?;ii]osc, erect or 

 peiiduloiis, internally with a tirm clioiidroid axis. Apothecia leca- 

 iiorine, peltate, terminal or lateral : spores Snip, small, simple, 

 colourless ; paraphyses not discrete. 8permogones immersed ; sterig- 

 mata simple or subsimplc. 



A natural tribe, distinoriiislied from its allies by having internally a 

 solid axis (as in Sfercoca it/on), which readily separates from the cortical 

 layer. Comprising only three small genera, two of which, ]\'eurojio(/on 

 and Chloren, do not occur in Great Britain, it is with us, as in most other 

 countries, marked by the abundance of the spjcies of Usnea. 



37. USNEA Dill. Muse. (1741) p. 56 pro parte; Ach. Meth. 

 (1803) p. 306. — Thallus filamentoso-elongate, or tibriUoso-ramulose 

 with patent branches, concolorous on both sides ; chondroid axis 

 composed of densely conglutinate filaments, cortical layer fragile 

 and often difiract. Apothecia concolorous or subconcolorous with 



Fig. 40. 



Vmi'd florida ke\\. — a. Longitudinal seotion of tlie tballus. x200. b. Vertical 

 section of a young apotbecium (with thalline receptacle). x30. c. Theca and 

 paraphysi?, x35d. d. Spores, XoOO. e. Transverse section of the thallus, 

 sliowing above a spermogone (beneath wliieh is a section of the medulla), 

 X30. /. Sterigniata and .spermatia, XoOO. 



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. 8permogones 

 lateral, slightly protuberant, in colourless conceptacles ; spermatia 

 straight, cylindrico-acicular, slightly incrassate towards the base. 



