(75 ) 
The spore-history of Collema, as the genus is here taken, makes indeed 
one of the chief points of interest and question in this otherwise closely 
associable group. Exhibiting, in the majority of species, what we cannot 
but regard as the muriform type, this type, in Collema, is notwithstand- 
ing constantly decolorate, and passes imperceptibly (earlier conditions of 
differentiation, occurring in the same species which exhibits finally the 
muriform, as in Arn. Lich. Fragm., in Flora, 1867, t. 2, f. 26, 31, becom- 
ing fixed, as in Arn. 1. c. f. 69-76, 93) into its opposite, the acicular. 
The passage is imperceptible, and the cluster in which elongated spores 
are typical (Synechoblastus, Auctt.) is thus as untenable as it is (in its 
type) wellcharacterized. Nor does this extraordinary exhibition of what, 
looked at from the point of view of perhaps the best understood lichen- 
groups, must be called anomalous development end, without showing 
pretty clearly that if Collema proper and Synechoblastus pass mutually 
into each other, and the latter may in fact be called only a marked, 
finally inordinate presentation of the earlier stages of spore-differentia- 
tion of the former, even the earliest stage is implied in it also; in such 
forms as Collema pycnocarpum, Nyl., (Sym. p. 115) as compared with its 
next of kin, C. cyrtaspis (Obs. Lich. 1. c. 5, p. 387). Thus viewed, Col- 
lema may well appear a natural assemblage, of whatever rank; and the 
anomalies of its spore-history, as of its thalline structure, as only the 
outcome of modifications which first meet us, if not in Peltigerei, at least 
in Pannariei; and recur, in part, so far as the spore-anomalies are con- 
cerned, in large groups (as Thelotrema) otherwise most widely separated 
from it. 
We may be unable to claim for LEProGiuM, Fr., any better limits than 
have been found for other generical groups, and its distinctness has been 
called in question even by recent writers;! but, leaving out of view con- 
fessedly ambiguous forms, looking perhaps equally towards Collema, or 
even Pannaria, there will still remain the large, richly differenced, and 
yet congruous assemblage, which Fries separated, and almost all writers 
since him have accepted; and this it is doubtless difficult to arrange sat- 
isfactorily otherwise than by itself. As respects the great bulk of Lepto- 
gium, it may be said to be characterized by muriform-multilocular spores 
which are always, as in Collema, entirely without colour. The irregular 
differentiation of the spore-type remarked in the latter genus recurs how- 
ever again here, where species with fusiform-acicular spores represent, 
more sparingly, Synechoblastus; and the earlier stages of the regular 
1“ Teptogium et Collema inter se omnino confluunt.” Nyl. Animadv. (Bot. 
Zeit. 1861, p. 337). “Die Gattung Leptogium, von Collema nur durch das Vorhan- 
densein einer zelligen Corticalschicht unterschieden, wird jedenfalls in Zukunft 
Sallen miissen, da einerseits Leptogien-Arten vorkommen, denen diese Corticalschicht 
fehlt, andererseits dieselbe bei gewissen Gallertflechten vorkommt, die nicht in die 
bisherige Familie der Leptogieen gezogen werden.” Koerb. Parerg. p. 422, & 
conf. p. 420. 
