(155 ) 
ents abroad, emboldens the present writer to hope he has, in any degree, 
attained. 
As understood then by many recent authors, Biatora (as here taken) 
falls apart into five distinct groups, received as genera, exhibiting the 
successive changes in the differentiation of the originally simple, colour- 
less spore; the first two, in which the spore continues simple, differing 
only in the thallus being either effigurate (Psora, Mass.) or granulose 
(Biatora, Mass.). But the process of differentiation tends always to its 
completion, and the stage of this process exhibited in Biatora, as thus 
restricted, is not by any means without fore-shadowings of succeeding 
ones. These find distinct expression in, first, the bilocular modification, 
or in Biatorina, Mass.; and then in the 4-8-locular (Bilimbia, De Not.). 
And the last of all, into which Bilimbia imperceptibly passes, and the 
acicular spores of which exhibit the perfection of the colourless spore- 
type, is Bacidia, De Not. The polysporous, biatorine lichens (upon 
which the remarks already made under the polysporous section of Leca- 
nora may be compared) are also separated, by the same authors, as Bia- 
torella, De Not.; &c. From the point of view of the present treatise, 
neither of the just-named genera can be accepted as valid; and it is not 
always that we find satisfaction in availing ourselves of them even for the 
construction of sections. The effigurate group (Psora) which begins the 
list of biatorine lichens, and the polysporous group (Biatorella) which 
may end it, correspond indeed interestingly with the similar sections of 
Lecanora: with regard however to the whole remainder, or great bulk of 
the genus, as here taken, it is plain that we have but a single series of 
most closely related forms; inseparable, in fact, but as species, by any 
character, but the inadequate and now sufficiently arbitrary spore-char- 
acter. The groups exhibiting the several stages in the evolution of the 
originally simple spore are smaller in Lecanora, and it is perhaps easier 
to restore Dimerospora, Lecania, and Ophioparma to their ancient places, 
than the corresponding, larger groups which have been separated from 
Biatora ; but the principle is the same. 
With present information, and it being understood, here as elsewhere, 
that Mexican species are but little known, I reckon the number of North 
American species of Biatora, as thus constituted, at about sixty; some 
brief review of which, in the order of the divisions just indicated, may 
now follow. 
Of the elegant group of effigurate lichens, making the first section 
(Psora) only two,— B. Russellit, Tuckerm. (Obs. Lich. 1. c. 4, p. 417, sub 
Lecid.) an inhabitant of lime-rocks, and B. rufo-nigra, Tuck. Syn. Lich. 
N. Eng. p. 58, of granitic,— are as yet known to me to occur commonly 
throughout the United States; and B. lurida and testacea, of the calcare- 
ous rocks of Europe, as well as B. albilabra, are wanting. ——B. globifera 
(Ach.) Fr., reckoned indeed as North American by Acharius, and an 
inhabitant of Greenland (J. Vahl) according to Dr. Th. Fries, has only 
