(105 ) 
author, and (similarly taken, and excluding in particular Urceolaria 
scruposa) the Parmelia sect. Placothalle of Fries’s latest revision of the 
Scandinavian Lichens. The more modern variations from this construc- 
tion have been determined by the microscope; Rinodina being separated 
by its distinct type of spore from Lecanora, and Placodiwm from both the 
others, as well by its sporal structure (exhibiting the polar-bilocular sub- 
type) as its multi-articulate sterigmas.——Lecanora, which is directly anal- 
ogous, as respects the great mass of its species, with Parmelia, affords 
the type of the sub-family. From this centre, Placodiwm diverges, in the 
colourless series, exactly as Theloschistes in the Parneliei; and Rinodina, 
in the coloured, as Physcia. Though strictly crustaceous, and indeed as 
regards the by far greater number of forms, granulose, the group offers 
many marked instances of a tendency to revert to a higher (thalline) 
structure; but such intermediate conditions (as Squamaria & Placo- 
dium of authors) are here less typical, and, in accordance with the Acha- 
rian conception, as anew presented by Stizenberger, subordinated. 
XXVII.—PLACODIUM (DC.) Naeg. and Hepp. 
Naeg. & Hepp in Hepp Flecht. Eur., t.2, et passim. Tuckerm. Obs. Lich. 
1. c. 6, p. 265; Lich. Calif. p.18; Lich. Hawai. p. 4. Anz. Catal. Lich. 
Sondr. p. 39, addita Gyalolechia, p. 38. Nyl. Lich. Scand. p. 135, 
addita Lecanora sect. A, p. 140. Stizenb. Beitr. l.c. p. 171, addita 
Lecaniz sect. ult. saltem pro p., ibid. Lecanora sect. Rinodina pr. p., 
et sect. Placodium, pr. p., Ach. L. U. p. 77. Parmelia sect. 3, pr. p., 
et sect. 4, pr. p., Fr. L. E. p. 114, 161, 123. Theloschistes pr. p., 
Norm. Con. p. 16. Physcia pr. p., Ricasolia, Fulgensia, Gyalolechia, 
Solenopsora, Pyrenodesmia, Callopisma, Candelaria pr. p., Blastenia, 
Xanthocarpia, Biatore sp., et Biatorinz sp., Mass. Opp. varr. in locis. 
Amphiloma, Psoromatis sp., Candelaria pr. p., Callopisma, Blastenia, 
Biatore sp., et Biatorine sp., Koerb. Syst. Amphiloma, Gyalolechia, 
Ricasolia, Psoromatis sp., Candelaria pr. p., Callopisma, Pyrenodes- 
mia, Xanthocarpia, Blastenia, Biatore sp., et Biatorinz sp., Koerb. 
Parerg. Xanthoria pr. p., Gyalolechia, Caloplaca, Blastenia, Biato- 
rine sp., et Biatore sp., Th. Fr. Lich. Arct.; Gen.; & Lich. Spitzberg.; 
in locis. Placodium, Callopisma, Biatorine sp., et Lecidez sp., Mudd 
Man. Brit. Lich. Placodii sp., Amphiloma, Thalloidimatis sp., Calo- 
plaea, Biatore sp., Patellarie sp., et Blastenia, Mill. Principes de 
Classif. 
Structuram exposuerunt Tulasne, Mém. sur les Lich. p. 61, 150, 
153, 161; Fuisting, de nonnull. apoth. p. 22, 27. 
Apothecia subscutelleformia, lecanorina, 1. pseudo-biatorina mar- 
gine 1. proprio 1. composito, disco plerumque luteo-aurantiaco. 
Sporee ellipsoidez, polari-biloculares (rarius normaliter biloculares, 
rarissime simplices) incolores. Spermatia oblonga 1. bacillaria; 
14 
