2. C. homalotropa A. L. Sm.—Thallus white, smooth, very-
thin, subdetermiiiate. Apothecia black, moderate, urceolate,
becoming plane, prominent, with a thick elevated m a rg in ;
hypothecium thin, blackish; paraphyses slender, lax, branched
above, colourless; epithecium dusky, subrugose ; spores 8 in the
ascus, colourless, elongate-cylindrical, multiseptate, the septa a t
slightly irregular intervals, 0,130—140 mm. long, 0,0045—50 mm.
thick.—Lecidea homalotropa Nyl. in Mora 1. p. 329 (1867);
Cromh. Lich. Brit. p. 9 0 ; Leight. Lich. PI. p. 337 ; ed. 3, p. 361.
Very closely resembles the preceding, but differs slightly in the
apothecia, which are generally plane, larger and somewhat rugose.
Hal. On the bark of old ash trees.—D-isir. Local and rare in
S.W. Ireland.—B. M. Between Killarney and Kemnare, and on the
Eagle’s Island, Lake of Killarney, Kerry.
Subtribe V. L L C ID L L I Nyl. in Plora Ixv. p. 458 (1882).
Thallus foliaceous, squamulose, crustaceous or with upright
podetia. Apothecia discoid or patellate, occasionally difform,
with proper margin o n ly ; spores usually eight in the ascus,
sometimes fewer or numerous. Algal cells (gonidia) Oliloro-
pliyceae.
The Lecideei differ from the Lecanorei in the absence of any algal
cells in the apothecia. There are four British Natural Orders :—
I. G V R O PH O R A C E ^ . — Thallus leafy, expanded. See
G y b OPHOREI (P a rt I. pp. 321-334).
II . CLAD0NIACEA3.—Thallus of two kinds : basal, of leafy
squamules, and upright, of simple or branching podetia, which
often open out into cup-like expansions (seyphi). See Ol ADODET
(P a rt I. pp. 107-181, 184-186).
I I I . CCENOGONIACE./®.—Thallus filamentous.
IV . LECIDEAOEiB. — Thallus crustaceous or minutely
squamulose.
O r d e r I I I . CÍENOGONIACEJE.
Thallus filamentous and byssoid in small patches, or forming
■widely spreading layers. Apothecia with a proper margin ; asci
8-spored; spores colourless, simple or 1-septate.
Thallus with Trentepohlia gonidia. 68. Ccenogonium.
Thallus with Cladophora gonidia. 69. E a co d ium .
68. CCENOGONIUM Ehrenh. in Horie PhysiciB Beroh p. 120
(1820). (PI. 2.)
Thallus composed of loose branching filaments, usually
brightly coloured. Algal cells Trentepohlia, forming a central
strand which is closely invested by irregularly branching fungal
hyphse. Apothecia apical or lateral, shortly-stalked, discoid
not carbonaceous; paraphyses discrete, unbranched, sometimes
faintly sep ta te ; spores eight in the ascus, colourless, fusiform or
elliptical, simple or 1-septate. Spermogones with fusiform
straight spermatia.
This genus belongs almost exclusively to warm regions; it is
represented in Europe by one species.
1. C. ebeneum A. L. Sm.—Thallus brownish-black, forming
a wide-spreading soft felt of much-branched filaments which are
constricted a t short intervals; algal cells Trentepohlia aurea,
surrounded by dark-brown fungal hyphse which closely follow
the outline of the alga. Apothecia not seen.—G. germanicum
Glück in Flora Ixxxii. p. 268 (1896). Conferva ehenea Dillw.
Conf. t. 101 (1809). Ghroolepus ebeneus Ag. Syst. p. 36 (1824) •
Hook, in Sm. Engl. FI. v. p. 381. Cystocoleus ebeneus ThwaitL’
i^sAnn. Mag. Nat. Hist. ser. 2, iii. p. 241, t. viii. B. figs. 1-3
The species is probably not uncommon, and, in damp localities, it
spreads extensively over the substratum in round patches or in a
radiating fan-like manner. The thallus is often invaded by a whitish
Leprana, which grows in scattered granules over the older parts of
the hohen. I t has been frequently confused with Bacodium ruvestre ■
so th at It IS impossible for the most part to determine the plants
recorded by the older writers. Byssus petrma nigerrima fibrosa
(observed by R. Richardson) Dill, in Ray Syn. Stirp. Brit. ed. 3, p. 57
n. 8 (1724), and quoted in Dill. Hist. Muse. p. 9, t. 11 f. 18 (1741)’
may be either plant. Byssus nigra Huds. PI. Angl. ed. 2, p. 606
(1778), Engl. Bot. t. 702, and Dematium rupestre S. F. Gray Nat.
Arr. i. p. 588 (1821), share the same uncertainty. Filaments are
occasionally found intermingled with the alga Trentepohlia aurea.
Hab. On rocks and stones, in shady localities.—Hisir. Somewhat
rare in Great Britain.—B. M. Llanymawddwy, Merioneth; Bridge-
north, Shropshire; Sychnant, Conway, Carnarvonshire; Bolton
Woods, Yorkshire; Kirkoonnel, Springkeli, Dumfriesshire; near
Rillin, Perthshire ; Loch Morar, Inverness.
69. RACODIUM Pers. Syn. Fung. p. 701 (1801). (PI. 3.)
Thallus composed of loose, branching filaments, dark-coloured.
Algal cells, Cladophora, forming a central strand, the fungal
hypha? growing in straight lines, and forming a closely investing
outer sheath. Apothecia and spermogones unknown.
1. R. rupestre Pers. I. c.—Thallus brownish-black, felt-like,
usually occurring in small patches, more rarely wide-spreadino-;
filaments straight, not constricted, branched, fungal hyphse very
dark-coloured, obscuring the central algal strand.
As stated above, this plant has been frequently included with
Ccenogonium ebeneum under the comprehensive name Byssus nigra.
B 2