40 
10. On Lecidea petrea, Flot. 
(a)—On basalt, the Wrekin, Shropshire, in Leighton’s 
Exs., No. 783 (sub num. Lichen rimosus, Dicks). The 
parasitic Verrucaria rimosicola, Leight. (Mudd, Brit. Lich., 
p- 308, pl. 5, fig. 179), which Korber describes as _affect- 
ing the thallus of var. sub-concentrica, Fr. (Parerga, 
p- 467), is scattered over the whole thallus as a series 
of very minute, black papille, quite like those of many 
spermogonia externally. It has, however, dark olive or 
brown, oval, 4-locular sporidia ; while the spermogonia of 
L. petrea, according to Tulasne, are small, black, punctiform 
conceptacles scattered among the apothecia, containing very 
delicate, straight spermatia about 000043” long, borne on small, 
irregularly ramose, sterigmata. In Leighton’s Exs. No. 184 
I found these spermogonia as minute, black papille scattered 
on some of the small, sterile thalline areole. ‘The spermatia 
were linear-oblong, borne on long, very slender, linear, fili- 
form, sterigmata, branching simply at base, and varying 
greatly in length. The basal cellular tissue was scarcely 
coloured brown. 
(6) On what appears to be merely a form of L. petrea 
(Lecidea calcaria, Weiss, Hepp’s Exs., No. 147; Diplotomma 
calcareum, Mudd, Brit. Lich., p. 219), on limestone from 
Yorkshire, collected by Dr. Carrington in 1857, are scattered 
Pycnidia,| which may be referable to Verrucuria rimosicola. 
Mudd (Brit. Lich., p. 308) describes the said Verrucaria as 
occurring on his Diplotomma calcareum, but he makes no refer- 
ence to pycnidia. The pycnidia of the Yorkshire Lichen are 
small, black, punctiform conceptacles scattered here and there 
on the thallus, containing stylospores, which are oblong-oval, 
borne on short, simple basidia. The same pycnidia appear 
to occur in my copy of Leighton’s Exs., No. 17 (var. 
concentrica), on sandstone, Llangollen, Denbighshire. In 
Scherer’s Exs., No. 184, Lecidea calcaria is accompanied by 
what appears to be the same Verrucaria, which here occurs, 
however, on the bare rock. The sporidia are those of 
V. rimosicola—brown when old. 
(c) With, or on, LZ. petrea in Scherer’s Exs., No. 183, 
occurs a series of small papille, externally resembling 
spermogonia. But they contain sporidia that are brown in 
maturity, normally 4- though sometimes 2-locular, ellipsoid, 
colourless in the young state (in the asci). Both asci and 
1 Vide “ Observations on W. Greenland Lichens,” p. 368, plate lii, fig. 37. 
? Ibid., p. 367, plate ], fig. 18. 
