REPRODUCTION OF THE LICHENS. 439 



thrown off from the thiiUus, it directly grows into a new 

 individual. 



The other organs are of more complicated structure, and 

 until recently, their significance was by no means fully 

 understood. The Spermogonia were first recognised as being 

 distinct organs by llzigsohn,^ who believed them to be aa- 

 theridia containing motile antherozoids. Tulasne, however, 

 pointed out that the spermatia with which they are filled are 

 not motile, and that the movement observed by Itzigsohn 

 was merely molecular ; he considered that they were com- 

 parable to the non -motile antherozoids of the Floridese. 

 More recently Cornu^ has shown that spermatia may be in 

 duced to germinate when they are placed under favorable 

 conditions, and he is therefore inclined to regard them as 

 conidia developed in special receptacles, which differ from the 

 ordinary conidia in size only. In the introductory para- 

 grajihs of his paper Stahl argues in opposition to the views 

 of Coruu that the fact of their having germinated is no abso- 

 lute proof of the non-sexual nature of the spermatia, and he 

 appeals to the growth of pollen-tubes in solutions of sugar 

 in support of his argument.^ He also points out that Cornu 

 was unsuccessful in inducing the germination of spermatia 

 derived from lichens. The facts upon which Stahl bases 

 his argument in favour of the sexual nature of the spermatia 

 of lichens will be stated in considering the development of 

 the apothecia. 



The structure of the Apothecia had been carefully inves- 

 tigated and described by Tulasne in his above-mentioned 

 work. Schwendener* had shown that the hyphae from which 

 the asci were developed were independent of those which bore 

 the paraphyses, and Fuisting^ had distinguished the former 

 group of hyphse as " ascogenous hyphse," and had shown that 

 the excipulum and the paraphyses were developed from the 

 same kind of hyphal filaments, but no accurate knowledge 

 as to the very earliest stages of their development had been 

 obtained until the publication of Stahl's researches. Possibly, 

 as he himself points out, the early stages of development 



' ' Bot. Zeit.,' 1850. Up to this time the Spermogonia had been 

 regarded as distinct genera of Liclieiis, Pyrenotheca (Fries), Thrombiiim 

 (WaUroth), jubt as the Soredia had been regarded by Acharius as forming 

 the genus Variolaria. 



2 'Ann. d. Sci. Nat.,' ser. vi, t. iii, 1876. 



* See the recent observations of Tomaschek, " Ueb. die Entwick. der 

 PoUeupflanzchen des Colchicuur Autumnale." ' Silzber. d. k. Akad. d. 

 Wiss.,' Ixxvi, 1877, Wien. 



* 'Flora,' 186i. 



^ 'Bot. Zeit.,' 1868. 



