PLACODEI. 835 
Series V. Placodei Nyl. Mém. Soc. Cherb. vii. (1855) p. 175. 
Thallus variously crustaceous, sometimes evanescent, rarely en- 
tirely wanting ; medullary layer, when present, usually cretaceous. 
Apothecia lecanorine, lecideine or biatorine, or lirelleform ; para- 
physes discrete or coherent, rarely not distinct. Spermogones with 
various sterigmata and spermatia.—Placodee Nyl. Mém. Soc. Cherb. 
li. (1854) p. 13, 
A very extensive series comprehending by far the largest number of 
Lichens. It is very variable in the characters of the thallus and fructifi- 
cation, though the tribes of which it is composed are in both these respects 
-related to each other by connecting links. The less developed thallus, 
the absence of a distinctly filamentose medullary layer, and the inferior 
type of the apothecia distinguish it from the precéting series. The thallus 
is rarely hypophleodal, and the apothecia are rarely parasitic. 
Tribe XVIII. LECANO-LECIDEET Nl. Flora, 1882, p, 458. 
Thallus crustaceous; laciniate, squamose, granulose or pulveru- 
lent, sometimes but little visible, occasionally absent ; internally 
rarely entirely cellular, containing gonidia, rarely gonimia; hypo- 
thallus more or less distinct. Apothecia lecanorine, lecideine or 
biatorine, occasionally difform. Spermogones with jointed or simple 
sterigmata. 
This comprises the numerous species of the Lecanoret and Lecideei, 
formerly in the Nylanderian arrangement regarded as distinct tribes. 
They are now, however, more naturally united into a single tribe from 
the circumstance that in some instances lecanorine apothecia are not to 
be distinguished from lecideine ; while in certain cases normally biatorine 
apothecia occur in species otherwise entirely referable to the Lecanoret. 
The tribe is primarily divided into six subtribes (one of which, Heppici, 
does not occur in Great Britain), differing from each other in the fructifi- 
cation. 
Subtribe I. PANNARIEL Nyl. Flora, 1882, p. 458. 
Thallus squamulose or granulose, rarely monophyllous, cellular in 
texture, containing gonimia, which are usually somewhat monili- 
form. Apothecia either lecanorine or biatorine, rarely lecideine ; 
spores 8n, colourless, simple or variously septate; paraphyses 
discrete, often thickish, generally articulate. Spermogones with 
jointed sterigmata. 
A subtribe well characterized by the structure of the thallus. Since it 
contains gonimia it holds much the same position in this as the Peltigerei 
in the preceding series, though the texture is otherwise very different. 
56. PANNARIA Del. in Dub. Bot. Gall. (1830) p. 606; Nyl. 
emend. Flora, 1879, p. 860.—Thallus laciniately divided or squa- 
mulose. Apothecia lecanorine ; spores ellipsoid or oblong, simple ; 
hymenial gelatine variously tinged with iodine. Spermogones with 
spermatia somewhat short, cylindrical, slightly thickened and obtuse 
at either apex. 
