BRITISH LICHENS

DIRINA DIRINACEJE 219
A small family represented in the British Isles by a single genus
and speCIes. It IS classified under Graphidinero on account both of
thalline and apotheeial characters, and is nearly allied to Roccellacero,
as was pointed out by Crombie in Monogr. i. 491 (1894).
Spores fusiform, 3.septate .. colourless ............ 83. Dirina.
83. DIRINA Fr. Syst. Orb. Veg. 244 (1825). (PI. 17.)
Thallus crustaceous, continuous or cracked. Apothecia
discoid or somewhat irregular or elongate, subimmersed in the
areolro or superficial, with a distinct thalline margin; hypothecium
thickish, black; spores 8 in the ascus, elongate-fusiform,
4-8-septate, colourless.
A maritime genus of few spccies but of wide distribution in warm
of subtropical regions.
1. D. repanda Fr. l. c.; NyI. in Mem. Soc. Sci. Nat. eherb.
ii. 313 (1854).-Thallus determinate and subeffigurate, thick,
continuous or areolate, generally unequal and coarsely wartedgranulate,
greyish-white with a soft farinose surface and a white
hypothallus (Kf + yellow, CaCI + rose-red). Apothecia moderate
in size (up to 2 mm. across), at first closed then plane, black,
covered generally with a white pruina, the thalline margin thick,
obtuse, more or less infiexed; hypothecium thick, black; paraphyses
simple, slightly widened or irregular upwards; spores
fusiform, often slightly bent, 3-septate, generally about 22 !L
long, 5 !L thick, but sometimes smaller or larger; hymenial
gelatine wine-red with iodine.-Cromb. in Journ. Bot. ix. 178
(1871) & Monogr. i. 491, fig. 69; Leight. Lich. FI. 235; ed. 3,
226. Parmelia repanda Fr. Lich. Eur. 177 (1831).
Exsicc. Johns. n. 421.
A Mediterranean plant chiefly. The apothecia are often crowded
and become difform, with the margin flexuose. Spermogones are
abundant.
Hab. On rocks in maritime districts.-Di8tr. Rare in the Channel
Islands, S.W. England and N. Wales.-B. M. La Coupe and Rozel,
Jersey; Portland Island, Dorset; Great Orme's Head, Carnarvonshiro.
Family XXIII. ROCCELLACEJE.
Thallus mostly fruticose, of strap-shaped or rounded branching
fronds, attached to the substratum by a basal sheath, corticate,
with a central medulla generally of loosely interwoven hyphre.
Algal cells Trentepohlia. Apothecia discoid or somewhat elongate,
usually with proper and thalline margins; spores 8 in the
ascus, colourless or rarely brownish, .elongate, septate. Spermoganes
with simple or sparingly branched sterigmata and straight
or curved aerogenous spermatia.