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serving, on the other, to render clearer the connexion of still more widely 
aberrant members of the tribe and family. 
Thus viewed, the Lecanore/ fall easily into three sub-families, distin- 
guished by well-marked differences in the fruit. In the first of these, or 
Eulecanorei, the tribal type is more or less exactly expressed by the apo- 
thecia, and the thallus also often reverts towards that of the Parmeliei, 
so that questions may arise as to the dominant affinity of certain of its 
forms, conceivable even as descending from certain other foliaceous ones 
(as Placodium from Theloschistes ;) and, taken by itself, the group is not 
without its difficulties. But these are only varied, and far enough from 
wanting, in our second sub-family —Pertusarie/—to which might even, 
at first sight, be refused a place in the tribe. The ‘naked nuclei’ of 
Pertusaria are yet certainly conceivable as nucleiform hymenia, imbedded 
in the typically compound, wart-like but Parmeliaceous apothecium of 
the genus; and such explanation of this extraordinary fruit is supported 
by the tendency of various forms to revert to lecanorine types, and finds 
what appears its complement in P. bryontha (a Lecanora in fact in all but 
the spores) and even (as compare the lucid description of LD. tartarea vy. 
pertusarioides, Th. Fr. Lich. Arct. p. 100) in Lecanora itself. The 
instance last-cited is by no means the only one in which the typical Par- 
meliaceous apothecium, at one stage or other of its development, antici- 
pates or illustrates that of Pertusaria; but it is perhaps the most 
interesting, as occurring in a group which is approached equally by 
recedent forms of the other. Pertusariei then, in whatever respects 
inferior to the sub-family here immediately preceding, is superior in 
interest in the fruit; this affording the extremest modification conceiva- 
ble of the Lecanora-fruit, within the clear limits of the tribal type. The 
spores of Pertusaria afford possibly another criterion of the affinity of 
the genus to Lecanora ; and serve also to distinguish it from otherwise 
now nearly related forms, which are presented, in a wonderfully varied 
series of even more difficult modifications, passing finally, one might 
almost say, into Biatora and Pyrenula, in our last sub-family —the 
Urceolarici. 
The number of distinct forms included in the Lecanorci, as here 
taken, is very large; embracing possibly not far from half of all compre- 
hended in the present tribe, which approaches more distantly to a not 
very dissimilar numerical relation to the whole Class. 
Sub-Fam. 1.—EULECANOREI. 
Apothecia scutelleformia. 
Adding the species of Urceolaria, Ach., with simple spores, the group 
represents exactly (exceptis excipiendis) the genus Lecanora of this 
