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G. Babingtonii (Mont.). And the argument from Graphis is, at any 
rate, sufficiently direct against the distinction of Volvaria (Massal. Ric. 
p. 141. Stizenb. Beitr. 1. c. p. 163) from Thelotrema ; and equally against 
the separation of Bombyliospora from Heterothecium. Otherwise, indeed, 
if a specific difference be to be admitted between the two forms of Arthonia 
cyrtodes, and the latter of them referred to Arthothelium, Mass., the 
former should not lack plausible claims to stand for a new genus. 
It might seem possible to regard Opegrapha,—if we omitted to con- 
sider the little group (Nyl.in Prodr. N. Gran. p. 92) with bilocular, brown 
spores, represented at the north by 0. lentiginosa, and by several, better 
developed forms in the tropics,—as belonging to the colourless series ; 
perfect spores being, in most species, more commonly colourless, and 
coloration being possibly quite unknown in some, and the differentiation 
generally resembling that of this series, the acicular type of which is 
indeed almost reached :—but the difficulties in the way of excluding the 
brown-spored group are far from slight ; while Thelotrema offers numerous 
instances of analogous discrepancies in a genus, the spores of which may 
be taken, and by an induction perhaps sufficiently general, to be typically 
coloured. Might we not, in short, beforehand expect that large, natural 
genera, developed mainly in the tropics, and abounding in external vari- 
ations from their types, should exhibit similar ones in their internal 
features? Opegrapha is afterall but a wing of Graphis ; distinguishable 
perhaps, but, strictly speaking, scarcely distinct. The eminent writers 
who have carried out this view, and regarded the whole of the first section 
of Graphis, as here taken, or even the first two sections, excluding tropical 
subsections of the last, as generically inseparable from Opegrapha, have 
yet excepted (Fries however, in S. 0. V., only with hesitation) Graphis 
proper (our third section) as, at any rate, distinct. But it proves, if Iam 
not greatly mistaken, quite impossible, in the present state of knowledge 
of the genus, to maintain this exception; and the third section must 
follow, therefore, the fortunes of the other two. If then we are content, 
here, to leave Opegrapha apart from Graphis, it is only as next toit; and 
as, at all events, a member of the same spore-series. 
Taking, as it seems to be safe to do, the whole number of clearly dis- 
tinguishable, and for the most part reckoned specific forms of Graphis, 
as here understood, described by authors, as a hundred and fifty, one 
eighth is known to occur beyond intertropical regions. But of this eighth 
the larger part is also properly tropical; and the proportion is seen then 
to be very small which belongs to the temperate zones. No species pene- 
trates the polar regions. Of the six forms inhabiting Europe, five occur 
within our limits, or all except G. Lyellii ; and we possess also one other 
northern Graphis, unknown elsewhere. Southward, thirteen tropical or 
sub-tropical Graphides, one of them not indeed here confined to the 
southern states, have thus far been detected. 
Of the first division (family, or stock of G. scripta) five species (as I am 
