(114) 
separable from the var. versicolor, Nvl. (Lich. Scand.) was found in 
Missouri (Prof. C. U. Shepard) and in Kansas (Mr. Hall). 
It is acknowledged, even by those who accept the generical distinction 
of the squamulose-etiigurate type of thallus (Psoroma, Auctt., Placodium 
1, Squamaria, Auctt.) of the Lecanore?, that there is no satisfactory di/- 
Jerence between this and the granulose. The passage of the latter into 
scales, prolonged at length into lobes, which revert again to squamaceous, 
or even granulose conditions, takes place within one and the same circle 
of crustaceous decline. And the centre, embracing the great bulk of the 
forms included in this circle being granulose, we may claim to explain 
excentrical conditions by the seldom wanting links which connect them 
with the ordinary, crustaceous type. This centre of the Eulecanorei we 
have now reached, in the section Eulecanora proper. As here taken, the 
group includes by far the larger part of the granulose Lecanore, Ach.; 
and, with similar exceptions, determined for the most part by the 
microscope, the most of Parmelia sect. Patellaria, Fr. We remove how- 
ever ZL. cinerea from this to the next following section, and add to the 
present those species of the section Uvrceolaria (Fr.) which only differ in 
their composite or zeorine margin. This latter overgrowth makes the 
only important exception to the general regularity of the scutelleform 
apothecium in Hulecanora ; and it is one clearly of subordinate account. 
Not only are we put to it, as Dr. Th. Fries has remarked (Lich. Arct. p. 
99) to distinguish Z. Cenisia even specifically from LZ. subfusca; but 
admitting the zeorine group in its narrowest sense (Zeora, Koerb.) two 
genera must also be recognized in the cluster represented by ZL. ventosa. 
As respects the spores, the present section, in the great majority of 
its species, is directly analogous with Parmelia ; and exhibits the primary 
(simple) condition of the colourless type. But the complexity of sporal 
structure is apt (as often remarked) to increase with the degradation of 
the thalline; and ELudecanora, though sufficiently true for the most part 
to its analogical relations, yet offers exceptions of no little interest. These 
exceptions are still far from being dignified by other accompanying 
differences of structure; and they illustrate in fact only the typical differ- 
entiation of the same spore, of which the remaining species exhibit the 
earlier stage. ZL. aipospila (Dimerospora, Th. Fr. Lich. Arct. p. 97) 
scarcely differs in the character of its spores from the rock-lichens to 
which it is otherwise most nearly related, except as the bilocular state of 
Placodium fulgens, or the bilocular spores of P. vitellinum, from the 
simple ones. Nor is it easy to see, if the next following step in the differ- 
entiation, represented by L. athroocarpa, Dub., Nyl. (Lecania fuscella, 
Massal.) be separated generically, how we can avoid distinguishing, in the 
same way, the analogous stage of development of the polar spore; of 
which Placodium Brebissonii, and the Physcia hypoglauca of Nyl. Syn. 
(t. 8, £51) afford instances. And when the dactyloid spore, passing 
easily into the fusiform, becomes finally attenuated into the acicular, I 
