202 LICHEXACZI, [rSXEA. 



The species are more or less social, occurring in wooded regions, cliiefly 

 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 trmiks 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 hchenologists, following Fries, have usually included several dis- 

 tinct species as varieties under V<nea harhata Fr., supposing that they 

 were connected bv intermediate states. Xylander has, however, a^aia 

 separated these, and pointed out that there ai*e sutScient external and 

 anatomical differences to entitle them to rank as distinct species — one of 

 the more important characters being the size of the spores. Xearly all 

 the species are often sorediiferous, especially in barren specimens ; while 

 on the thalli of several " cephalodia " are not unfi'equent. 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. S'yn. i. p. 266j. The spermogones are 

 rare and covered by the thallus, on which they appear as slight protuber- 

 ances, Avith spermatia 0,009 mm. long, about 0,001 mm. tliick. 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 Xatm-alist, vi. p. 101 et seq.). 



1. U. florida Ach. Meth. (1303) 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, 0-0u7-ll mm, long, 0,006-7 mm. thick. — 

 Gray, Xat. Arr. i. p. 403 ; Hook. Fl. Scot. ii. p. 70 ; Sm. Eng. FI. 

 V. p'. 226 ; Cromh. Journ. Linn. Soc. Bot. xvii. p. 555. Usnea har- 

 hata a. florida Mudd, Man. p. 69, t. i. f. 15; Cromh. Lich. Brit, 

 p. 23 ; Leight. Lich. Fl. p. 83, ed. 3, p. 75 : Tayl. in Mack. Fl. Hib. 

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

 Angl. p. 463 ; ^\ith. Arr. ed. 3, iv. p. 50 ; Eng. Bot. t. 872. 

 Usnea vulr/atusima tenuior et hrevior, cum orhicidis Dill. Muse. 69, 

 t. 13. f. 13. Liclienoides quod Museus arhoreus cum orbiculis Dill, 

 in Eay Syn. ed. 3, p. 65, n. 6. — JBnt. Exs. : Cromb. n. 16. 



Easily recofmized 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. AVhen several plants gi-ow 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 nigulose 

 and shortly fibrillose on the imderside. 



Hab. On the branches of trees, rarely en-atic on rocks, in upland 

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

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

 in the Channel Islands : not seen from Ireland, thougli said by Dr. Taylor 



