36 



AN ABSTRACT OF 

 M. BORNET'S PAPER ON THE GONIDIA OF LICHENS.* 



By W. Phillips. 



M. Bornet begins his paper by describing the structure of the 

 thallus in Lichens, as consisting of a colourless filamentose tissue, 

 termed hypha, and a coloured cellular portion, termed gonidia, 

 remarking that for a long time past the great similarity of the 

 gonidia to certain algEe had been observed, but that recent 

 researches have thrown much additional light on the subject, 

 tending to show this similarity to be not merely superficial or 

 confined to a few isolated instances. M. Schwendener, in his 

 various papers on the subject, has traced the resemblance of the 

 gonidia to eight types of alga?, four of which belong to the group 

 Nostocacece, and three to Chlorophyllophycece. 



Different methods have been suggested of accounting for the 

 resemblance thus traced. Some have regarded it as a simple 

 coincidence, others have looked upon the algre which correspond 

 with the gonidia as imperfect or sterile states of true lichens, while 

 a third party have advanced the startling theory that a lichen is a 

 complex structure consisting of a particular kind of fungus living 

 parasitically upon an alga. M. de Bary was the first to suggest this 

 theory, but it was M. Schwendener who gave it shape and threw 

 around it an air of probability. This learned savant states that he 

 saw the filaments of the lichen-thallus (the hypha) penetrate the 

 fronds of different algas (Sirosiphon, Nostoc and Glceocapsa) ; en- 

 compass the gonidia with a network, similar to that with which a 

 spider entangles his prey, and in a certain number of genera 

 {Jtoccella, Arnoldia, Lempholemma, and P armaria) unite themselves 

 to the gonidia by an actual junction. 



M. Bornet aims at confirming this theory of parasitism, looking 

 upon it as the only one capable of explaining satisfactorily all that 

 has hitherto been observed, and attributes its non-acceptance 

 among Lichenologists to M. Schwendener having failed to dwell, 

 as much as he ought to have done, on the nature of the connexion 

 existing between the hypha and gonidia, and the mode in which it 

 is established. Here appears to be the whole gist of the question. 

 To demonstrate the identity of gonidia with algge is the first point ; 

 but it is not decisive, as is proved by the opposite interpretations 

 of the fact by MM. Famintzin and Baranetzky, who equally with 

 M. Schwendener admit this identity. It is indispensable to show 

 that the relations of the hypha to the gonidia are such as neces- 

 sarily imply the idea of parasitism, and that these relations cannot 

 be otherwise understood. To this point M. Bornet specially 

 directs his observations, candidly admitting that it is one of the 

 most difficult investigations that can be met with in the whole 

 study of microscopic anatomy. 



* " Annales des Sciences Naturelles," 5e serie, tome xvii., ler Cahier. 



