RECENT RESEARCHES INTO THE NATURE OF LICHENS. J49 



In the 'Comptes Eendus ' for November, 1874, H. A. Wed- 

 dell draws attention to the Lichinese as being very favorable 

 objects for observations of this kind. The gonidia not only 

 form the greater part of the thallus of the Lichens, but they 

 regulate its form. The hyphse lie in the gelatinous investment 

 and bear the apothecia. Such Lichens have been termed pseudo- 

 algae. Unfortunately this term has been extended to those 

 Algae which the opponents of Schwendener's theory regard as 

 imperfect Lichens, that is, as gonidia ; such are Stigoneraa and 

 Scytonema. If it can be proved that there are true Algse, one 

 of the strongest objections to the theory would be overthrown. 

 He considers that such evidence has now been collected. The 

 researches of Janczewski, and of Thuret and Bornet, upon the 

 reproduction of Nostoc by spores demolish the argument that it 

 is an imperfect or a modified form of Collema; and the re- 

 searches of Bornet (see ante) upon the gonidia of Opegrapha 

 have the same effect. He then brings forward a communication 

 made by Gibelli to the Botanical Congress held at Florence 

 (May, 1874).! Gibelli had observed the formation of zoospores 

 in the gonidia of Lecanora suhfnsca while still in the thallus. 

 This observation Weddell says enables us to account for the so- 

 called spontaneous appearance of gonidia in parts of the thallus 

 where none had previously existed. Gibelli also confirms Bornet's 

 experiments on Opegrapha. 



At a meeting of the Societe Botanique de France, held on 

 November 27th, the physiological aspects of the question were 

 discussed. M. Cornu opened the subject by saying that the 

 peculiar parasitism exhibited by Lichens was not sufficient ground 

 for separating them from other Ascomycetes. Such a parasitism 

 exists also in other families of the same group, as, for example, 

 that of Spharia cupularis upon the red stroma of Nectria 

 cinnabarina, and again, of Aster osp or mm Hoffmanni upon Cticur- 

 bitaria macrospora. M. Weddell pointed out that in these 

 examples the two organisms belonged to the same family group 

 of plants, whereas in Lichens it was a cohabitation of organisms 

 belonging to different classes. The term "parasitism^' if used 

 to describe this cohabitation is used in a forced sense, for the liost 

 instead of suffering grows the more vigorously. 



M. Cornu, in reply, referred to the observations of Bornet, 

 from which it appears that the form of the Alese is somewhat 

 modified under the influence of the hyphae. M. Weddell rejoined 

 that in Collema and its allies the hyphae do not come into contact 

 with the cells of the Nostoc filament, and that, moreover, the 

 modification of the Alga in other Collemaceae under the influence 

 of the hyphae is not such as could forbid the assumption that the 

 ' ' Atti del. cong. iulern. bot. Firenze 1876.' 



