202 LICHENACEI. [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, a^ain 

 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 et 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 : Sin. 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. 

 ii. p. 86. Lichen floridus Linn. Sp. PI. (1753) p. 1154; Huds. Fl. 

 Angl. p. 463 ; With. Arr. ed. 3, iv. p. 50 ; Eng. Bot. t. 872. 

 Usnea vulyatissima tenuior et brevior, cum orbiculis Dill. Muse. 69, 

 t. 13. f. 13. Llchenoides quod Museus arbor eus cum orbiculis Dill, 

 in Kay Syn. ed. 3, p. 65, n. 6. Brit. Exs. : 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. 



Hub. On the branches of trees, rarely erratic, on rocks, in upland 

 woods and forests. Distr. General and not uncommon in Great Britain, 

 but move frequent and fruiting more freely in the Southern tracts ; rare 

 in the Channel Islands ; not seen from Ireland, though said by Dr. Taylor 



