208 DR LAUDER LINDSAY ON THE SPERMOGONES AND PYCNIDES 
layer, which has been eroded, exposing the subjacent white, medullary tis- 
sue. So much so is this the case, that the plant is scarcely recognisable as 
P. caperata. Apothecia, which are usually rare, are here abundant. ‘The sper- 
mogones are punctiform and immersed—black when dry, brown when moistened ; 
they are most irregular as to size and form, often chink-like, sometimes confluent. 
They are dotted over the rugose or warted portions of the thallus ; but they are 
most conspicuous on the white eroded portions, their brown colour forming a 
good contrast to the white of the medullary tissue. The body of the organ is 
spherical, and its cavity simple. 
Specimen 2.—Fermanagh, Ireland; Dr Scorr, 1803; wood, near Camelford, 
England, 1799; in Herb. Hooker, Kew. The thallus is coarsely warted, the 
warts or rugosities being studded over with punctiform spermogones, as in No. 1. 
Specimen 3.—Tasmania, very common; OLpFIELD; in Herb. Hooker, Kew. 
The spermogones are more distinct and abundant in this specimen than in any 
others of this species I have examined. They are distributed chiefly centrally on 
the thallus, but to a minor extent peripherally, and on specimens not bearing 
apothecia. The thallus is very rugose, and often consists centrally of a series of 
large cushion-like warts, which are abundantly studded over with spermogones, 
resembling parasitic Sphwrie. These spermogones are comparatively large, 
black, round rings or spots, superficial, flattened, varying in size, sometimes con- 
fluent and irregular, never distinctly papillate. In the centre of these rings or 
spots are the simple, round ostioles. The envelope is of a sooty black colour; 
the body of the spermogone is easily enucleated. The spermatia are acicular, 
about ja;th to sth long, and ;;;th broad. Korper very erroneously describes 
them, as in this species atomic and globular, which they certainly never are, 
according to my observations. ‘The sterigmata usually consist of two, or not 
more than three, elongated linear cells, articulated at irregular angles; their 
length is about th. The spermogones, which occur about the more flattened 
and simple margins of the thallus, are more usually simply punctiform, and 
wholly immersed ; nor are they so crowded as centrally. 
SPECIES 2. P. perlata, Ach. 
Almost a cosmopolite, as well as its well-marked but puzzling variety, ciliata, 
DC., which occurs in Europe, Africa, America, Asia, and Australia. This is a very 
variable lichen. Many forms of it, especially var. ciliata, so strongly resemble 
Platysma glaucum as to be constantly mistaken therefor ; others closely resemble 
forms of P. sinuosa, tiliacea, and other species. It passes into the next species, 
P. perforata, which | regard, indeed, as a mere variety of P. perlata. Its sper- 
mogones are generally black, punctiform, immersed, and scattered about the 
margins of the lobes of the thallus. Its spermatia are acicular and of medium ~ 
size ; its sterigmata are composed of a few linear articulations. 

