36 



meliffi, the isidiophorous American states of which differ so much 

 from the smooth European lichens, that, when Isidium was not yet 

 understood, they were reckoned distinct species. (P. rudecta, Ach. = 

 P. Borreri, 'Yurn.,isidiophora.) The formation of Isidium is not found 

 to be common to species otherwise allied, nor to all genera ; it is 

 wholly wanting among the inferior, the Myco-liehenes, and is, 

 indeed, generally peculiar to the Parmeliacese and Endocarpe, 

 in two northern states of the former of which, an isidio-morphous 

 thallus seems to be normal. Perfect apothecia are commonly 

 wanting in strongly marked isidioid states, but rudimentary devel- 

 opments or globules, often of a brownish hue, the result of an 

 atypical metamorphosis of gonidia, occur frequently at the apices of 

 the branches. The consummate descriptions of Turner and Borrer 

 (Lichenogr. Britt.) afford the best view of Isidium, Variolaria, Le- 

 praria, and Spiloma, that has been given. It is, moreover, manifest 

 that these eminent botanists anticipated those views of anamorpho- 

 sis now so well understood, (which others, indeed, had also, to some 

 extent, foreseen,) and had even received and extended somewhat 

 the rudiments of the true doctrine of the gonidia. Among the 

 many other forms of thalline anamorphosis, we can in this place 

 refer only to that remarkable and perplexing prolification of the 

 thallus, the Lichen parasiticus of E. Bot. (Endocarpon parasiti- 

 cum of Acharius, and well described by Sommerfelt as Lecidea 

 Parmeliarum). This forms minute, lobed, from cucullate, explanate 

 leaves, varying from bluish green to glaucous, which grow caespi- 

 tosely from the original thallus, and are often besprinkled here and 

 there with hemispherical black cephalodia, much like the apothe- 

 cia of Lecidia. It has been found to occur on several different spe- 

 cies of Parmelia ( Imbricaria), in each case participating more or 

 less in the color and nature of the matrix, and with us is often ob- 

 servable, with all the above features, in P. Borreri. 



We have now to consider the anamorphoses of the apothecia. 

 These originate in a suppression of evolution, and have been made 

 to characterize (of course while they were not understood) not only 

 spurious genera of lichens, but even species of fungi. In some 

 forms of Spiloma, to be hereafter described, spurious apothecia are 

 formed by a semi-complete metamorphosis of gonidia. Besides 

 this, the principal abnormal states which we have to notice are, 



I. Angiocarpous states of Gymnocarpi, when, that is, the normal 

 evolution of the apothecia is broken off, and we have atypically persis- 

 tent the original nucleiforrn apothecium (q. v.), which, by further de- 

 generation, is yet more altered. Various supposed species of Endo- 

 carpon, Porina, and many SagediaB of Acharius are thus referable to 

 imperfect states of Parmelia3,while other Sagedi and Pyrenulse have 

 arisen from abortive Lecideae. It has been already remarked, that 

 when apothecia arise from the cortical layer, the nucleiform, or disci- 

 form thalamium is more exserted, and appears primarily without any 

 excipulum ; if their further evolution be impeded, these rudimentary 

 apothecia become blackish, and similar to the perithecia of Verru- 

 caria or Sphseria, to both which tribes anamorphoses of this kind 

 have been referred. And this is almost universally the explanation 



