Bory in Duperrey, Fog. Bot. p. 240. Mont, in Voy. cm Pole Sua 1 , Bot. Crypt, p. 201. U. sphacelata, Brown, in Parry, 1st Voy. App. p. 307. Hook. Plant. Arct. in Linn. Soc. Trans, vol. xiv. p. 384. Bot. Miscell. vol. i. p. 1 5. 1. 12. U. fasciata, Torrey, in Sillhnan Journ. vol. vi. cum ic. Hook. Bot. Miscell. vol. i. p. 14. 1. 11. U. aurantiaco-atra, If TJrv. in Mem. Soc. Linn. Paris, vol. iv. p. 596. Cornicularia flavicans, Persoon, in Freyc. Toy. Bot. p. 210. Lichen aurantiaco-ater, Jacq.Miscell. (fid. Acharius).
Yar. a. Acharii; robusta, thallo scabrido, apotlieciorum marginibus nudis. — U. melaxantka, Ach. I. c.
Var. /3. Jacquinii ; robusta, thallo hem. — Lichen aurantiaco-ater, Jacq. I. c.
Var.y.fajciala; robusta, thallo tuberculato, ramulis pluries divisis capillaceo-attenuatis, apotheciis extus tuberculatis. — U. fasciata, Torrey, I. c.
Var. 8. sphacelata ; gracilis, thallo laevi pruinoso v. tuberculato fruticuliformi ramosissimo, ramulis eapillaribus. — U. sphacelata. Broion, I. c.
Hab. Throughout Tierra del Fuego and the Falkland Islands ; on exposed rocks, from the sea to 2,000 feet, most abundant. New South Shetlands ; Webster, Br. Bights.
Perhaps the handsomest of all Lichens, whether we regard its colour, stature, or mode of growth, and yet so variable in all these points, that the extremes are scarcely recognizable. In size it varies from a few lines or an inch, with capillary stem and branches, to four inches, with a woody stem a quarter of an inch in diameter. The colour is sometimes wholly (especially in var. 8) black, at others uniformly yellow, but most frequently banded with black, especially towards the apices of the ramuli. Old specimens turn tawny red, as do all when, after being dried, they are soaked in warm water. The apothecia are yellow, grey "or deep black. The surface of both the stems and the back of the apothecia is more or less tuberculated or pruinose, smooth or much wrinkled, naked or more or less covered with longer or shorter horizontal terete acuminated ramuli. The apothecia vary exceedingly in breadth, from two or three lines to almost half an inch; their margins are smooth, tuberculated or beset with branching ramuli; they are generally terminal, but the younger appear lateral when subtended by a branch.
It is in the Falkland Islands that this species most abounds, covering the surface of the Quartz rocks with a miniature forest, seeking the most exposed situations, and there attaining its greatest size and beauty. In these Islands, too, all the five varieties I have enumerated may be collected within a few feet of one another, and so associated as to leave little doubt that they are states depending on age, rather than marked races. The var. 8. especially, is certainly only an undeveloped state, which does not bear soredia in the Antarctic regions; or apothecia either in Tasmania or in the Arctic latitudes, where soredia are produced.
The structure of the stem of this, and probably of some other Lichens, presents a marked analogy with that of the Laminarioid Algse described at p. 460, The central thread is very large, composed of concentric layers of dense, horny, red cellular tissue, gradually passing into a soft white pith, enclosing a cavity. Around this horny thread, whose edges are sharply defined, are arranged concentric layers of a spongy cellular substance, which again are enclosed in a cortical layer, as dense as the central, and to which the yellow and black hues of this Lichen are always confined. Thus, proceeding from the circumference, there is — 1st, a horny, coloured, cortical layer, answering to what is called the cortical layer of Lessonia, and to which, in that plant also, the coloured chronmle is chiefly confined ; 2nd, the layers of intermediate lax tissue, successively deposited, though much more obscurely so than iu Lessonia ; 3rd, the central thread of Usnea which is a stout axis, answering to the elliptic core of Lessonia, but in this Lichen becoming so lax towards the centre as to enclose a cavity in the older stems.
We have never observed spores in any specimens of this Lichen, from whatever place collected, though we have examined very many apothecia in a live state, as well as after being dried, both young and old, and of all colours, both black, grey, or yellow. Dr. Montagne (Voy. au Pole Sud, 1. c.) has been similarly unsuccessful.
