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and there into conterminous, or sub-tropical regions. Following Fée, 
Nylander places here the sometimes differently understood G. grammitis 
(Diorygma, Eschw. Fissurina, Mont.) which may be said, possibly, to 
look in one direction towards the coloured Medusule or Ustalie, and in 
the other towards forms closely associable with G. frumentaria. 
The aspect of the best developed conditions of the remaining small 
group (Lissurina, Fée, Diorygma, Eschw.) as G. Babingtonii (Mont.) and 
G. nitida, is that of the last ; and there is certainly noimportant difference 
in structure between the species named and G. grammitis ; which, as 
already cited, has been reckoned congenerical with them by most eminent 
lichenographers. But G. grammitis is not so easily removable from the 
neighbourhood of G. chlorocarpa; and though the walls of the exciple 
be less easily discernible in the Fissurine proper, an exciple is never, so 
far as the writer’s observation has gone, (and compare here Fée Ess. 
t.1, f. 7, #) in any absolute sense, deficient. Fissurina is then undistin- 
guishable from Graphis; of the central type of which it may easily be 
regarded a colourless degeneration. Indeed in certain low forms common 
in the tropics, and referable here, Graphis may be said, perhaps, to reach 
its extremest degradation; nothing appearing to the naked eye, or even 
to an ordinary lens, but certain paler cracks in the bark upon which these 
humble lichens grow. 
Graphis differs generally from Opegrapha in its larger spores, some 
features in the differentiation of which are also distinguishable; the 
ellipsoid spore becoming now elongated and cylindraceous (eruceform, 
Koerb.) especially in the first group; and this elongated, or the ellipsoid 
state (with entire sporoblasts) passing readily and frequently into the 
muriform. And the natural assemblage before us affords, if I mistake 
not, no little evidence looking to shew not merely that the different grada- 
tions in the differentiation of the same spore-type may be exhibited within 
the limits of a single genus, but even within the circle of forms of one and 
the same natural species. There does not appear to be any important 
diversity between the two forms of Arthonia cyrtodes, Tuck. (Obs. Lich. 
1. c., 6, p. 285) except that in a, the spores (of the same type with, and 
when young undistinguishable from those of #) have not yet reached the 
perfection indicated in the latter. So Graphis sophistica, Nyl. (Steno- 
grapha anguina, Mudd Man. Brit. Lich. p. 235) repeats the forms of, and 
differs in no known respect from G. scripta, save that the now less elon- 
gated spore (when young quite similar to young conditions of G. elegans 
and G. scripta) exhibits finally the completion, as does G. scripta a less 
advanced stage, of the muriformtype. Compare further, as to this inter- 
esting point, G. anguilliformis, Tayl., Nyl. (in Prodr. Fl. N. Gran. p. 76, 
fig. 31, & in Herb. Lindig n. 2634) with G. vernicosa, Fée, as exhibited 
in the same publications; G. striatwla (Ach.) Nyl., with G. elegans ; 
G. hemographa, Ny). (1. ¢. p. 88, & in Herb. Lindig nu. 878) with G. cinna- 
barrina, Fée, of the same publications; and G. instabilis, Nyl., with 
