BRITISH LICHENS

12 CYCLOCARPINElE LECIDEA
sis tent or indistinct. Algal cells. Protococcaceoo. Apothecia
either light-coloured to dark-brown and biatorine, or black and
lecideine, the proper margin often obliterated; spores usually
eight in the ascus, ellipsoid or oblong, simple, colourless; hymenial
gelatine variously tinged with iodine. Spermogones with spermatia
acicular, straight, rarely arcuate, or shortly cylindrical.
This extensive genus has been grouped under four sections. The
spores are colourless and simple or rarely faintly I·septate; the asci
are 8· or more- sometimes 6-spored, excepting in the section Mycoblast'us,
whieh contains one species with a 1- or 2-spored ascus. The term
biatorine, from Biatora. has been applied to those apothecia that are
lighter in colour and soft in texture, while lecideine signifies the dark
almost black fruits that are carbonaceous and hard, and that belong
more particularly to the EulecideaJ. There is, however, no clear
line of demarcatlOn, as the colour and form of the fruits change with
age. The genus is very well represented in our islands, where a
considerable number of species seem to be endemic. The chemical
reactions, which have been given as far as possible, will be found to
be useful in distinguishing plants WhICh otherwise might readily be
confounded. The species have been grouped in four sections distinguished
by thalline or apothecial characters. In the first three
sections occur variable species that might be listed in either of the
other two.
Thallus distinctly squamulose .. , ...... § i. PSORA (1-16).
Thallus variously crustaceous.
Ascus 8-spored.
Apothecia lighter in colour ...... § i1. DIATORA (17-82).
Apothecia dark and carbonaceous § iii. EULECIDEA (83-209).
Ascus 1- or 2-spored.
Apothecia dark ..................... § iv. MYCOBLASTUS (210, Il).
§ i. PSORA Haller Hist. Stirp. Helv. iii. 93 (1768) et auctt.,
pro parte. (PI. 4.) Thallus gquamulose; spores 8 in the ascus.
Spermogones with simple sterigmata and straight spermatia.
1. L. )urida Ach. Meth. 77 (1803) & Syn. 51 (1814).-Thallus
imbricate, appressed, dull- or dark-brown (K -, CaCI-); the
squamules orbicular, rigid, sinuate-Iobed, dark beneath. Apothecia
superficial on the squamules, adnate, plane, brownishblack,
the margin obtuse, slightly flexuose, becoming convex
. and immarginate; hypothecium thick, dark-brown; paraphyses
stout, coherent, reddish-brown at the apices; spores ellipsoid
or oblong-ellipsoid, 13-15 [J. long, 5-7 [J. thick; hymenial gelatine
slightly bluish then wine-red with iodinc.-Hook. Fl. Scot. ii.
40; Carroll in Nat. Rist. Rev. vi. 525; Cromb. Lich. Brit. 64;
Leight. Lich. Fl. 252; ed. 3, 244. Lichen luridus Sw. in Nov.
Act. Upsal. iv. 247 (1784); Dicks. Crypt. fasc. ii. 20; With.
Arr. ed. 3, iv. 28; Engl. Bot. t. 1329. Lepidoma luridum S. F.
Gray Nat. Arr. i. 460 (1821). Psora lurida DC. Fl. FJ;. ii. 370
(1805); Mudd Man. 170. Lichenoides pulmonarius saxatilis
viridis l etc' l Dill. lIist, 1\11,1sc. 228 1 t. 30. f. 134 (1741).