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LY.—MYCOPORUM, (Flot.) Nyl. 
Mycoporum, Flot. in Koerb. Grundr. Nyl. Prodr. Gall. p. 171; Lich. 
Scand. p. 291; & in Prodr. Fl. N. Gran. p. 111. Th. Fr. Gen. p. 98. 
Lecides sp., Scher. Spicil. p. 199; Lich. Helv. n. 232; & Enum. p. 131. 
Rhizocarpi? sp., Massal. Ric. p. 103. Arthothelii sp., Koerb. Parerg. 
p. 261. 
Apothecia subcomposita, pseudo-stromate difformi nigro hymenia 
(1-plura) fovente. Spore (in thecis abbreviatis, subpyriformibus) 
oblongo-ovoider 1. oblongx, bi-quadri-loculares, 1. dein muriformi- 
multiloculares, fuscescentes 1. decolores. Spermatia haud visa. 
Thallus crustaceus, uniformis 1. hypophlceodes. 
The compound character assumed finally by Arthonia has been re- 
marked under that genus. Eschweiler was first to indicate this, referring 
the group, as he limited it, together with Coniocarpon, to his Trypethel- 
iacee, (Syst. p. 17) which included the compound types of both Graphi- 
dacet and Verrucariacei ; and when, later (Lich. Bras. l. c. p. 110) he 
places Arthonia at the end of his Graphidee, it is not without the sug- 
gestive remark, that ‘ob verrucas discolores pro stromute habendas nucle- 
orum rudimenta fovente,’ it should still seem to be properly associable 
with that section of the Trypetheling represented by Porothelium, Eschw. 
But interesting as is the appropriateness of the hypothetical character 
just cited to the present little cluster of arthonioid lichens, as understood 
by Nylander, we may notwithstanding doubt if Eschweiler would not 
rather have referred Mycoporum pycnocarpum, Nyl. (as compare Poroth. 
arthonioides, Lich. Bras. p. 153; & Syst. fig. 21) to his Porotheliwm ; as 
Flotow acutely suspected the same type in his I. elubens. 
It is indeed impossible quite to deny the existence of something like 
mutual approaches between the compound groups of Graphidacei and 
those of Verrucariacei ; and equivocal types, if we do not possess them 
already, might well be expected to occur. The reference of Mycoporum 
(Flot.) Nyl., to a different tribe from Mycoporum, Mey. (Porothelium, 
Eschw. pro p., Melanotheca, Fée pro p., Nyl. Tomasellint, Massal., Koerb.) 
does not affect the remarkable congruity of these types; and states of 
Mycoporum pycnocarpum, Nyl., are none the less better comparable with 
Melanotheca, Nyl., or, in aspect at least, with Verrucariaceous expressions 
like Trypethelium nigritulum of the same author (Lindig herb. N. Gran. 
n. 2794) than with anything Graphidaceous, because the latter affinity is 
in fact mediated by Chiodecton. 
From the genus last named, and the family represented by it, the 
present little group is, as in other respects, sufficiently distinguished by 
the want of astroma; and its real interest and significance appear rather 
tolie inits relations to Arthonia. In place of thestromatous modification 
of a thalline exciple, we have, in our representative of Mycoporwm, Nyl., 
