(150 ) 
We do not leave Cladonia, without passing, in the variations of 
C. squamosa, into what is technically Biatora; and Fries has given 
expression to this instructive fact in his Biat. Cladonia (L. E. p. 256). It 
is indeed as easy and natural to regard Cladonia, Beomyces, and Biatora 
as constituting one continuous series, as it is to conceive of Parmelia 
(upon which compare Norman Con. p. 14) and Lecanora as making such 
a series. The approximation of the two groups last named is yet 
interrupted by Pannaria, with all that its ultimate structure associates 
with it; and Caenogonium is here provisionally regarded as occupying, in 
Lecideacei, a place analogous to Pannariei, &c., in Parmeliacei. 
Montagne followed Fries in arranging the type before us with Ther- 
mutis, &c., but in whatever structural resemblances these plants agree, 
it is sufficiently evident that, in the present condition of knowledge, we 
are not entitled to class them together; and Canogonium must be 
excluded from Collemei. Its exclusion is less obvious, it is true, from the 
very anomalous and ill-defined Pannariei: and here we have also to 
note, as not without bearing in the same direction, that its apothecia are, 
whether externally or internally, not a little similar to those of the bia- 
toroid Gyalecta lutea; and that Nylander places it, in his Lecidee?, next 
before Gyalecta. 
The structure of the thallus of Cenogoniwm is not so simple, or Con- 
Jerva-like, as was at first predicated of the genus. We find, and in all 
well-ascertained forms, that the filaments are made up of 1, a central 
series of cylindrical cells, with green content considered to be chlorophyll, 
and 2, of slenderer, colourless thread-cells which longitudinally band, or 
at length loosely surround, the first. The first may be taken to represent 
gonidia (Nyl. Cenog.1.c. Schwend. 1. ¢.) and the second will then stand 
for the medullary filaments (Nyl.1.c. Hyphen, De Bary 1. c.). 
Ten species are reckoned by Nylander in his revision of the genus, all 
of them belonging to the warmer regions of the earth. Four of these 
oceur in Cuba (Wright) and I possess C. Linkti also from Mexico. C. in- 
terpositum, Nyl. 1. ¢., a native also of the island of Bourbon, was found, 
on trunks, in Louisiana (Hale) and is the only Cenogonium known as yet 
within the limits of the United States. 
Cystocoleus, Thwaites (Ann. Nat. Hist. 2, 3) founded on Racodium 
rupestre, Pers., is associable in structure with Cenogonium ; but is only 
known ina sterile condition. Fries observed that this plant was blackish- 
green when moist (Summ. Veg. Scand. p. 123) and it is the type of his 
emended Racodium (genus persistit tantum in prima specie, que vero a 
Fungis excludenda,’ Ibid. p. 521) to which he gave a place next to Ephebe ; 
but the peculiarities of its structure were first indicated by the English 
author cited. The axial part of a filament of Cystocoleus appears to offer 
nothing to distinguish it, in any marked way, from the same part in 
Cenogonium; and in the former equally with the latter, the pale-green 
