48 PROCEEDINGS OP THE AMERICAN ACADEMY 



Physma Mulleri to be a form of Collema myriococcum, leaving the 

 identity of the latter species with C chalazanum an open question. 

 In examining specimens of Physma Mulleri I have found a type of 

 reproduction identical with that seen in G. chalazanum, a spermogo- 

 niumat the base of which arise ascogonic cells prolonged outside of the 

 spermogonium in the form of trichogynes. (Plate VII. Fig. 37.) The 

 septa of the trichogynes exhibiting a progressive process of thickening 

 from above downwards, the sprouting of the ascogenous cells to form 

 asci, the pushing aside and suppression of the sterigmata by the growing 

 asci and paraphyses, and the final transformation of the spermogonium 

 into an urceolate apothecium embedded in the thallus, are points 

 which may be readily seen and followed in the species before us, 

 and they serve still further to connect it with C chalazanum. 



We are now in a position to adopt one of two views. It has been 

 shown that all the species of the genus Physma, Mass. (with the possible 

 exception of P. sanguinolentum Krmph.) are, according to accepted 

 methods of classification, to be grouped together as one or possibly two 

 species of Collema. We find, however, that these two species present a 

 distinct type of reproduction, essentially unlike that of many other spe- 

 cies of Collema. We must therefore conclude, either that this is really 

 a generic distinction, in which case the present genus Collema must be 

 divided, or else that in the one genus we have at least two modifica- 

 tions of the sexual type of rej^roduction seen in certain of the Flo- 

 rideae. The latter seems at present the more expedient. As yet the 

 sexual reproduction of certain lichens has not been accepted as a basis 

 of classification, and should it be so accepted certain species at least 

 of Leptogium would have to come under Collema, while Collema 

 would lose one or more species in favor of a new genus. A much 

 more extended knowledge of the gelatinous lichens must exist before 

 we can venture to state even that these two modifications of the type 

 of reproduction are the only ones which exist in the Collemaceai. 



I have further followed Stahl's investigations upon certain species 

 of Collema and Leptogium in which the spermogonia and apothecia 

 are separate, and the ascogonium exists as a simple coiled hypha 

 reaching the surface by means of a multicellular trichogyne, and, to- 

 gether with the neighboring hyph^e, developing directly into an apo- 

 thecium. Among the lichens provided with a cortex I have examined 

 only Leptogium myochroum, (Ehrh., Schaer.) Tuck., and it is only ne- 

 cessary to state that the points observed by me have been entirely 

 confirmatory of the results obtained by Stahl from his study of this 

 species and of L. microscnpicum. Here again, in the face of Stahl's 



