PYCNIDES OF CRUSTACEOUS LICHENS. 267 
Specimen 1. On oaks, Hopton, 1801, Dickson: associated with Arthonia impolita, Borr. 
The supposed Zecidea consists wholly of spermogones—minute, black, superficial, semi- 
immersed papille—retaining in age their papillæform character. Spermatia linear, 
straight or slightly curved, sooo X 3550: sterigmata very short, simple, and not over 
060 long. 
Specimen 2. From the same locality, exhibits spermogones only, unassociated with 
apothecia of any kind. In the young state they externally resemble those in No. 1; but 
they become flattened, irregular, and Arthonioid. Their sterigmata are the same as in 
No. 1; but the spermatia are subellipsoid, 355 X t0500- 
Specimen 3. Apparently on palings—labelled Relhan, 1801, without habitat. The 
thallus is thin, white, and pulverulent, bearing only spermogones, as small, black, round, 
superficial or slightly immersed, flattened, subdiscoid or subannular bodies, the disk, or 
centre, white-pruinose, the border more prominent from its blackness, giving them the 
aspect of a series of ill-formed black rings. The spermatia are subellipsoid, 3555 X 55-055: 
on very short, simple sterigmata. 
Under the specific name Z. dryina, several very different plants, or their organs, have 
been classed by authors. Thus, Z. dryina, Flk., is, according to Nylander (L. Scand. 
p. 249), a Schizoxylon (S. dryinum, Flk., a Fungus); while L. dryina, Rabenh. — Arthonia 
melaleucella, Nyl. (Scand. p. 261), which, again, = Pyrenothea stictica, var. lecidina, Er., 
and Trachylia melaleuca, Fr. L. dryina, Scheer., is, according to Körber (Syst. Lich. 
Germ. p. 299), Bactrospora dryina, Ach., which = Coniangium, Fw., and Coniocarpon, 
Rabenh. Z. dryina, Fr., according to Nylander (Scand. p. 249), =Schizoxylon corticolum, 
Fr., =Coniangium corticolum, Fr. 
Species 40. L. CANESCENS, Ach. (— Diploicia, Mudd, Brit. Lich. p. 169). 
Specimen 1. On bark of trees, Aghada, Cork Harbour, March, 1858, Carroll: in fruit. 
Spermogones are plentiful on some of the lobes near their periphery, as scattered, black, 
punctiform or papillzeform conceptacles, distinct by contrast of their colour to the grey 
or white of the thallus. In character they resemble those of Physcia stellaris. The 
spermatia are acicular, 3955 — 43955 X 332999» on arthrosterigmata, consisting of a few 
narrow delicate cellules. 
Specimen 2. On volcanic rocks about Agde: Scheer. Exs. No. 576. Here, again, the 
spermogones externally resemble those of Physcia stellaris, than which, however, they 
are greatly smaller, and with much more difficulty visible; they are sparingly scattered 
over the laciniæ, towards their ends, as small, round, black, subprominent tubercles, con- 
taining acicular spermatia, zooo long, borne on very delicate, closely aggregated sterig- 
mata, that are either, as in No. 1, eomposed of a few articulations, or are digitately 
divided as in 4brothallus oxysporus. 
Species 41. L. caxptpa, Web. (= Thalloidima, Mudd, Brit. Lich. p. 172). 
Specimen 1. Trigby Church, 1802: in the Kew herb., sub Lichen tumidulus, Sm. 
(which, according to Mudd, p. 173, — Thalloidima mammillare, Gouan!). Only spermo- 
