(12) 
offer what may well appear the structure of Usnea with much the habit of 
Ervernia; the Everniine habit being however, in two of the species (E. Ca- 
nariensis, and E. Poeppigii) confined to the apothecia; and the thallus, in 
these species, being externally also best comparable with that of certain 
Usnee. With all which, looking doubtless towards the separation of 
Chiorea, the rank of the new group is by no means as clear as its differ- 
ence. And it is worth considering that another first step in the transition 
of Evernia into Usnea is taken within what is universally accepted as 
Evernia itself; in the strikingly Usneoid £. divaricata (Usnea flaccida, 
Hoff.) the string-like medulla of which differs only in the degree of 
coherence of the filaments that make it up from that of Usnea. 
In view of the structural modification just considered, it cannot sur- 
prise us to find Frernia losing at length that softness which has always 
been taken for one of its characteristical features. The change is suffi- 
ciently evident in older as compared with younger portions of £. culpina; 
and in a not altogether dissimilar lichen of the Himalaya (Hook. et 
Thoms. Herb. Ind. Or. n. 1731. Chlorea cladonioides, Nyl.) the horn-like 
medulla of which makes up almost the whole of the thallus, this is in fact 
rigid. 
All four of the well-known northern species are found within our ter- 
ritory. ££. divaricata is confined to the Rocky Mountains, where it was 
first detected by Mr. E. Hall. £. vitlpinais also confined to North-western 
America, where it is exceedingly luxuriant on the coast, and extends east- 
ward, though here only infertile, as far as the Black Hills, Nebraska (Dr. 
Hayden). 
VI.—USNEA (Dill.) Ach. 
Ach. L. U. p. 127; Syn. p. 303. Eschw. Syst. p. 24. Fr. §. O. V. p. 234, 
sp. excl.; L. E.p.17. De Not. Framm. p. 26. Tuckerm. Syn. N. Eng. 
p. 7, sp. excl. Scher. Enum. p. 3. Tulasne Mém. sur les Lich. p. 27. 
Norm. Con. p.11. Mass. Mem. p.72. Speerschneid. in Bot. Zeit. 1854, 
pp. 193, 209, 233, t.7. Koerb. Syst. p. 2. Schwend. Untersuch. 1. c. 2, 
p- 110, t.1,2. Th. Fr. Gen. p. 47. Stizenb. Beitr. 1. ¢. p. 177. Par- 
melie sect., Mey. Entwick. p. 335. Wallr. Naturgesch. 2, p. 355; Fl. 
Crypt. Germ. 1, p. 541. Eschw. Bras. p. 226. Scher. Spicil. p. 499. 
Usnea et Neuropogon, Nyl. Syn. 1, p. 266, t. 8, f. 7-12. 
Apothecia orbicularia, peltata, disco thallo subconcolore, 1. rarissi- 
me discolore. Spore subellipsoidee, simplices, incolores. Spermatia 
bacillaria, apicem versus alterum fusiformi-incrassata, vel cylindrica; 
sterigmatibus subsimplicibus. Thallus fruticulosus dein pendulus 
filamentosusve, teres, undique similaris, medulla duplici, interiori 
indurata axem sistente lignosum, exteriori stuppea. 
The modification of thalline structure upon which, taken in connection 
with the colour of the apothecia, Nees and Flotow distinguished their 
