202 LICHEN ACEI. [USNEA. 
The species are more or less social, occurring in wooded regions, chiefly 
in old woods (though sometimes saxicole and lignicole), where, with their 
pale-greenish or yellowish thalli often very considerably elongate, they 
form, especially when fertile, a fine ornament to the trunks and branches 
of the trees, covering them as if with a “shaggy fleece.” The limits of 
many species have been little understood by recent authors, the earlier 
writers having in this respect a more accurate judgment. Accordingly, 
modern lichenologists, following Fries, have usually included several dis- 
tinct species as varieties under Usnea barbata Fr., supposing that they 
were connected by intermediate states. Nylander has, however, again 
separated these, and pointed out that there are sufficient external and 
anatomical differences to entitle them to rank as distinct species—one of 
the more important characters being the size of the spores. Nearly all 
the species are often sorediiferous, especially in barren specimens ; while 
on the thalli of several “cephalodia” are not unfrequent. These are 
lateral, pale, or at length brown, tuberculoso-pulvinate, solid, internally 
dense (with no distinct gonimic layer), and composed of thin, interwoven 
filamentose elements (vide Nyl. Syn. i. p. 266). The spermogones are 
rare and covered by the thallus, on which they appear as slight protuber- 
ances, with spermatia 0,009 mm. long, about 0,001 mm. thick. In the 
British species the cortical layer usually gives a more or less yellowish 
reaction with K, but is untinged by CaCl. Frequently, however, the 
positive reaction is very faint or even wanting in portions of the same 
specimen, so that it cannot be employed for the discrimination of species, 
as Dr. Stirton has done (Scottish Naturalist, vi. p. 101 e¢ seq.). 
1. U. florida Ach. Meth. (1803) p. 307 pro parte.—Thallus erect, 
rounded, scabrous, very much branched, pale-greyish or greyish- 
green; branches patent, nearly simple, with crowded horizontal 
fibrils. Apothccia plane, moderate or large, pale or somewhat glau- 
cous, ciliate at, the margins, the cilia long, fibrillose, radiating ; 
spores shortly ellipsoid, 0-007-11 mm. long, 0,006-7 mm. thick.— 
Gray, Nat. Arr. i. p. 403; Hook. Fl. Scot. ii. p. 70; Sm. Eng. Fl. 
v. p. 226; Cromb. Journ. Linn. Soc. Bot. xvii. p. 555. Usnea bar- 
bata a. florida Mudd, Man. p. 69, t. i. f. 15; Cromb. Lich. Brit. 
p. 23; Leight. Lich. Fl. p. 83, ed.3, p.75; Tayl. in Mack. Fl. Hib, 
li. p. 86. Lichen floridus Linn. Sp. Pl. (1753) p. 1154; Huds. Fl. 
Angl. p. 463; With. Arr. ed. 3, iv. p.50; Eng. Bot. t. 872. 
Usnea vulgatissima tenuior et brevior, cum orbiculis Dill. Muse. 69, 
t. 13. f. 13. Lichenoides quod Muscus arboreus cum orbieulis Dill. 
in Ray Syn. ed. 3, p. 65, n. 6.— Brit. Evs.; Cromb. n. 16. 
Easily recognized by its constantly erect habit, and the horizontal 
fibrils with which the branches are covered. The thallus is usually rigid 
and more or less scabrid. When several plants grow in proximity they 
form, with their large and numerous apothecia, a striking object on the 
forest trees, and present the appearance of a small parasitic shrub. The 
apothecia are terminal and smooth, though in age they become rugulose 
and shortly fibrillose on the underside. 
Hab. On the branches of trees, rarely erratic on rocks, in upland 
woods and forests.—Dzs¢r. General and not uncommon in Great Britain, 
but more frequent and fruiting more freely in the Southern tracts; rare 
in the Chanuel Islands; not seen from Ireland, though said by Dr. Taylor 
