lhallus of the matrix, either within or without it, and in the second, 

 bursting through the thallus irregularly, and in various ways alter- 

 ing and even destroying its whole habit. (Another anamorphosis 

 which is not to be confounded with that we are to describe, is that 

 produced by a change of the exterior cells of the cortical layer into 

 heterogeneous bodies (stauromata) already noticed, which often re- 

 semble, but are altogether different from soredia.) 



In a very common kind of gonidial anamorphosis, the thallus, as 

 it were, totally deliquesces, and the gonidia every where bursting 

 through the cellular layer above them, an expanded powdery sur- 

 face, consisting of gonidia intermixed with cells of the other strata, 

 is formed, which is what we call Lepraria. This is found in 

 crustaceous, foliaceous, and vertical lichens, occurring more or less 

 marked, and if sterile constituting the Acharian genus of the 

 above name, which name is now used only to denote this abnormal 

 condition of the lichenose vegetation. 



Or, again, if the gonidia break out in those regular powdery 

 heaps which we call soredia, (this evolution taking place atypically, 

 that is, contrary to the original type of the species,) and overrun the 

 lichen, the cells of the cortical layer adjacent are broken and 

 altered, the whole plant becomes sterile, and a monstrous habit is 

 induced, which we call Variolaria. The various forms of this, origi- 

 nating in different crustaceous (as most commonly in Pertusaria) or 

 even foliaceous lichens, constituted the Acharian genus of the same 

 name. Sorediiferous states of lichens cannot, generally, according 

 to Fries, even be considered varieties ; and he thus abolishes Ra- 

 malina farinacea (Lichen farinaceus, L.) as merely R. calycaris so- 

 rediifera ; and in the same way some other long-received and com- 

 mon species and varieties. But we find in the manner of appear- 

 ance of the soredia very great differences, and these diversities are 

 of more weight than the mere presence or absence of this develop- 

 ment Their importance is manifest in the case of the cyphellce of 

 Sticta, the most remarkable form of soredia ; and peculiar to a sin- 

 gle very natural genus. 



The two kinds of anamorphosis already described are common, 

 says Fries, to all Algse ; but we have next to notice one, peculiar, 

 it would seem, to lichens, those coralline, subcylindrical, elevated, 

 and here and there branched excrescences, which, appearing in and 

 covering more or less a crustaceous thallus, were reckoned, together 

 with the thallus in which they broke forth, forms of a distinct ge- 

 nus by Acharius, under the name of Isidium; a name still appro- 

 priated to this state of vegetation in lichens. The formation of 

 Isidium is attributed by Meyer to an elevation of the cells of the 

 cortical layer, by the protrusion of gonidia. It seems, however, 

 difficult to determine the relative action of the different layers in 

 the case with any certainty. A crustaceous thallus is often so much 

 altered by this anamorphosis, that its original habit is almost, or 

 entirely lost, and it is matter of praise, rather than censure, that 

 Acharius separated and collected all these states, as he did those 

 others already mentioned, but the very same development occurs 

 in foliaceous lichens, and is conspicuous in some of our largest Par- 



