PYCNIDES OF CRUSTACEOUS LICHENS. | 979 
mogones of two forms (quoad the size and shape of their spermatia), of the characters of 
those of Opegrapha vulgata, whose lirellæ, however, do not here appear. In one form 
the spermatia are crescentic, 3555 X 556060; on simple sterigmata, about 3755 long with 
spermatia attached. In the other, the spermatia are linear, straight or slightly curved, 
considerably smaller, 2555-5000 X 1500 By the older lichenologists, such spermo- 
gones, occurring in patches or groups by themselves, without lirellæ, apothecia, or peri- 
thecia, would have been classed under Pyrenothea, while by fungologists they would 
have been placed probably in Septoria*. 
Genus III. ARTHONIA. 
In general terms, its spermogones and pycnides resemble those of Opegrapha, both in 
external character and internal structure. The spermogones are usually very minute, 
brown or black, punctiform or papilleeform conceptacles, scattered more or less abun- 
dantly over the thallus. Sometimes, as in lurida, they are maculeform and round, 
. resembling its young apothecia. In punctiformis they are about 343 in diameter, with 
an ostiole yọ in diameter. The sterigmata are, for the most part, simple, or they 
branch slightly from the base, never articulated, their length usually about 3555 - 1665: 
The spermatia are almost always straight, linear, or linear-oblong, varying considerably 
in length, being from 55-305 in punctiformis, 5555-3060 in ilicina, but more generally 
greatly smaller, even subatomic, 55455 — rogov long. In certain forms of impolita they are 
ellipsoid; and in ¿licina, punctiformis, and some forms of impolita, curved or twisted, 
as in certain Lecanore (.L. subfusca) and Lecidee (L. parasema). Sometimes two or 
three forms of spermogone occur, as in Opegrapha (e. g. in A. cinereo-pruinosa.) Pye- 
nidest, also as in Opegrapha, are not uncommon (e. g. in astroidea and impolita). 
Species 1. A. ASTROIDEA, Ach. 
Specimen 1. Apparently on birch, Carrigaloe, Great Island, Cork harbour: Carroll, 
Oct. 1858. The apothecia are few, grouped, partly Verrucarioid, partly Lecideine, partly 
deformed; but the sporidia are of the usual character. Associated with the apothecia are 
spermogones, small, black, punctiform, with an envelope of slate-coloured cellular tissue. 
Spermatia rod-shaped, 7757 long, on short, simple sterigmata. 
Associated with the Arthonia and its spermogones, though not necessarily or even 
probably belonging to it, are numerous pycnides, supposed by Carroll to be those of Stri- 
gula Babingtonii, Berk. Externally they resemble the spermogones, being black, 
punctiform or papillzeform, and Verrucarioid conceptacles. They are very minute, and 
with difficulty detected, even by the lens. They are distributed sometimes over what is 
apparently a separate thallus, or they are seated directly on the bark. Occasionally they 
are flattened cones, sometimes girt with a thalline ring, usually inconspicuous when it 
occurs. Extreme variability of size and form (especially the latter) characterizes the 
stylospores. In the young state they are simple, and frequently pyriform, beeoming in 
* Vide first Mem. Spermog., pp. 107 and 120. 
+ Vide also paper on Arth. melaspermella, p. 271. 
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