(117) 
is appended to it in the General Enumeration of Nylander. We have 
throughout the southern country, from South Carolina (Mr. Ravenel) to 
Texas (Mr. Wright) upon bark, and also on rocks in New Mexico (Wright) 
the elegant, tropical L. punicea, Ach., which may serve to illustrate the 
proper affinity of the other more divergent members of the group, te 
Eulecanora proper. So closely does this species approach L. subfusca, 
that a form of the latter with similarly coloured disk, (comp. the v. 
erythrocarpa, Mont. Cub. p. 207) may well be undistinguishable from it, 
but by the spores, and spermatia. And the American representative of 
L. elatina, Ach., is most readily passed over, in some of its numerous 
forms, for L. subfusca, though in fact so well distinguished, as in other 
respects, by the composite exciple. The finer conditions of this lichen 
(Biatora dein Parmelia ochrophea, Tuckerm. Syn. N. E. p. 61, & Lich. 
Exs.n. 91, 111) are but ill-comparable with the rarely fertile European 
state; but the smooth, glaucescent thallus becomes at length leprous and 
ochroleucous, when nothing remains to separate it but its better devel- 
oped fruit. A possible form of this (Vermont, Mr. Frost) with thin 
smooth, dispersed thallus, and paler, minute apothecia which are more 
evidently pruinose than in the American state of a, is well comparable 
with published specimens of Hematomma cismonicum, Beltram. (Rabenh. 
Lich. Eur. n. 531). 
Thus far Lecanora is marked, as a whole, by the regularity of its apo- 
thecia ; and it is not difficult, in most cases, to explain aberrations. But 
this is far from being as easy in the two small, almost wholly repicoline 
groups which follow. In the first of these the innate apothecium is 
finally so modified that the very genus becomes doubtful, if not the 
tribe ; and even the most patient comparison of such modifications with 
the type to which they are referable, may fail (for want at least of suffi- 
“ ciently instructive specimens) of a satisfactory issue. Perplexing rock- 
forms occur however in other groups; nor is it necessary to go far to find 
an exact analogue of the one now before us, which is well known as 
Aspicilia. This analogue is furnished by the immediately preceding 
genus (Placodium), several species of which (as P. chalybeum and 
P. variabile; and also P. cinnabarrinum) differ from other species pre- 
cisely as forms of Aspicilia differ from EHulecanora; and are quite as 
separable from their otherwise natural allies. The section is indeed, as 
are other sections, more largely developed in Zecanora, and has received 
proportionate attention; but the difference (depending on the more or 
less innate apothecium) upon which its distinction is based, is no less a 
subordinate one in this, than in the other. 
L. cinerea is the well-known type of Aspicilia, and exhibits, or at 
least serves to explain, in mountainous countries, almost the whole circle 
of variations which distinguishes the group. From this, also effigurate 
in Arctic America, the radious ZL. circinata appears to me to differ much 
as Placodium candicans from P. chalybeum, or as Lecanora muralis 
