2GG EEV. J. M. CBOMBIE ON THE ALGO-LICHEtf HYPOTHESIS. 



upon Protococcus viridis *, and those of Lecidea muscorum upon 

 another species of Protococcus {vide Kecherch. sur les G-onidies, 

 &e.) ; while Treub sowed the spores of Physcia, Ramalina, and 

 Lecanora upon Cystococcus himicola (vide Memoir already cited, 

 pt. ii.). All these experiments, however, met with but a very- 

 limited amount of success, just as in the case of spore-culture 

 by itself without any added " algals." Even where tbe spores 

 successfully germinated and produced hypha?, all that could be 

 affirmed was that these formed with the Algae a structure re- 

 sembling in some degree the more or less rudimentary thallus 

 of a lichen But it is to be observed with respect to tbese syn- 

 thetical cultures, and all other experiments of a similar kind, 

 that even were the results more pronounced than they have 

 been, they would prove absolutely nothing as to the truth of the 

 hypothesis. The lichen-spore must, from its very nature, produce 

 lichen-hyphse, whether with or without the addition of algals or 

 pseudo-algals ; though what the fate of true added Algae in the 

 subsequent evolution of the thallus might be, the experiments 

 in Symbiosis do not show. A very singular synthetical experi- 

 ment was made by Dr. Stahl (vide Beitr. zur Entwick.-Gesch. 

 Elechten, 1877, Heft ii., " Ueber die Bedeutung der Hymenial- 

 gonidien "), which has been imagined in some quarters to supply 

 " the missing link " in the chain of evidence by which the Schwen- 

 denerian hypothesis can be demonstrated f- He cultivated the 

 spores of a lichen which he called Endocarponpasillum, Hedw. (but 

 which evidently was Verrucaria Garovaglii, Mont.), along with 

 the hymenial gonidia (more correctly gonidimia) which adhered 

 to or surrounded the spores %. Each spore sent forth from its 



# That this Protococcus constituted the gonidia of Thyscia parictina had long 

 previously been suggested by Kiitzing (vide Phyc. Gen. 1843, p. 167) ; but, as I 

 have elsewhere shown, it is a true algal, and has only a superficial resemblance 

 to any lichen-gonidia {vide Pop. Sc. Rev. 1874, p. 271, 1. 112. ff. 3, 4). 



t For a detailed and crushing reply to Stabl's observations and conclusions, 

 vid. Ricbard's valuable treatise, ' Etude sur les substratums des Lichens ' (1883), 

 pp. 6-13. 



X These hymenial gonidimia have an " intraconceptacular origin " (vide Nyl. 

 in Flora, 1877, p. 357), evidently originating from the parietal cellules of the 

 pyrenium in which tbey arise before the thecfe. Consequently they do not 

 find their way in after the formation of the " tubule " and by the open apo- 

 thecia, as Schwendener affirms in the conclusion of his paper " On the Gonidia 

 question," Like the gonidimia of the thallus, they no doubt act chiefly as 

 vivifying stimulants. 



