354 
There is a most unnecessary sectioning of genera, accord- 
ing : usually, to the simplicity or complexity of the spore. 
Were the structure of the spore constant it might be made 
a very convenient basis for dividing genera into sections, but 
certainly not for splitting genera like Lecidea into a host of 
independent genera. The character of the spore is not, how- 
ever, constant, even in the same species ; it is, e. g., fre- 
quently, even in the same plant, simple, or 2- or more-locu- 
lar : in which case a given Lichen, such as Lecidea vernalis 
or anomala, is artificially referred to one genus, while it 
belongs, in another sense, at least to two, and perhaps to 
more ! 
The most anomalous genera in the preceding list are 
Celidium, Phacopsis, and Phymatopsis, which are really in- 
termediate in characters between the Lecidece and Graphidece. 
But they may with propriety, I think, be referred provision- 
ally to Arthonia, so long as that genus is the very hetero- 
geneous one it is, and includes so many Lecidioid forms like 
A. melaspermella. 1 2 
The most diverse views are frequently adopted by differ- 
ent observers as to the character of the same Lichen and its 
place in classification. Moreover, the opinions of the same 
author are constantly undergoing variation. Hence it fol- 
lows that the most extraordinary changes occur in the 
nomenclature of the same plant, with a corresponding confu- 
sion of synonymy. The changes and confusion in question, 
relating both to genera and species, are represented especially 
by the following species : and this confusion would be much 
more apparent if I had access to all the published con- 
tributions of continental authors on the group of parasites 
now under review : — 
Lecidea parasitica, micraspis, sagedioides. 
Tichothecium gemmiferum, pygmceum, Arnoldi. 
Microthelia rugulosa, rimosicolar 
Abrothallns Smithii, oxysporus. 
Arthonia varians. 
Sphinctrina turbinata. 
Acolium coralUnum. 
Xenosphceria Engeliana. 
Karschia talcophila. 
Scutula Wallrothii. 
1 Vide author’s paper on A. melaspermella, ‘ Journ. Linn. Soc.,’ “ Botany,” 
vol. ix, p. 274 ; and ‘ N. Z. Licli. & Fung.,’ 449, 450. Stizenberger appa- 
rently arranges Phacopsis under Lecidea (‘ Beitr. z. Syst.,’ 162). 
2 i am utterly at a loss to understand on what grounds Nylander alters 
the name of this well-known Lichen to Verrvcaria advemda! (q. v.) 
