264 DR LAUDER LINDSAY ON THE SPERMOGONES AND PYCNIDES 
mata in which often become so hypertrophied and so aggregated as to fill the 
whole spermogonal cavity with a dense coloured tissue. But the phenomenon 
also is of frequent occurrence in mature spermogones; and the abnormal or ex- 
ceptional condition, I should say, is the absence, not presence, of these peculiar 
filaments. ! 
Specimen 4.—Var. ecrustaceum (sub Placodium Agardhianum ; syn. Lecanora 
Agardhiana, Ach. ScHRER exs. 617; on limestone, in the Jura and Alps) ; Hepp. 
exs. 407. The apothecia are black, flattish, or sub-convex bodies, with an indis- 
tinct, thin, evanescent border. Accompanying or intermixed with these, are 
bodies of the same size, flat or sub-convex, without any distinct exciple, having 
frequently a ragged or notched edge. They are of a whitish or buff colour, have 
quite the aspect of apothecia, are white-pruinose, like the apothecia and spermo- 
gones of Lecidea abietina, and are generally semi-immersed in the limestone on 
which the plant grows. They are really spermogones, though outwardly very 
unlike these organs in their ordinary forms; and they are the largest bodies of the 
kind with which I am acquainted. The spermatia are ellipsoid or linear-oblong, 
about jouth long, and .ja0th broad. The sterigmata are longish, delicate, arti- 
culated, about ;,th to yoth long, and jqnth broad. The spermogones are not only 
white-pruinose on their surface, but are whitish and mealy throughout. The 
apothecia are occasionally also white-pruinose externally, and they are then dis- 
tinguishable from the spermogones only by microscopical examination. The 
spermogones, however, are always lecidine, the apothecia lecanorine; but this 
distinction may not at once strike the eye. 
Species 3. P. chalybeum, Duf., Neg. 
In his “ Prodromus Lichenographice Galliz et Algerize,” 1857, p. 81, NyLAN- 
DER arranges this species with the Lecanoras having simple sterigmata. This does 
not at all accord with my observations; the sterigmata in all specimens examined 
by me, as is also the case in all the species of P/acodium, were articulated. His 
removal of this species to the genus Placodium, in his “ Enum. Générale des 
Lichens,” 1858, p. 111, may, however, be regarded as a confession of error. 
Specimen 1.—HeEpp. exs. 204; on calcareous rocks. The spermogones are 
plentifully scattered over the whitish or grayish areole; they are punctiform, 
immersed, grayish or blackish; with a raised, lighter, broken thalline margin. 
The spermatia are rod-shaped, atomic in size, on arthrosterigmata. 
Specimen 2.—ScHERER exs. 566 (sub Lecanora chalybea) ; on calcareous stones 
about Montpellier, and in the Eastern Pyrenees. The spermogones are whitish 
small tubercles, with a pale-gray ostiole of the same colour as the thallus, not 
easily recognised even under the lens. They somewhat resemble the spermogones 
of Lecidea fusco-atra, both in site and in external appearance. The spermatia are 
very abundant, rod-shaped or ellipsoid, jz.qth long. 

