180 THR JOUKNAL OF BOTANY 



difficult to speak of mutual service. Even in ISfiS Schwendener in 

 his investigations on the colour-changes of the blue-green algse of 

 lichens came to the conclusion that the fungus was a parasite upon 

 the alga. Bornet also regarded the relationship between the fungus 

 and alga as one of parasitism of the former, owing to the results of 

 his convincing investigations on the destruction of the blue-green 

 algae by fungus hyphse. Experiments with prepared cultures did 

 not really give sufficient reason for the assertion of mutualism or 

 antagonism between alga and fungus, but, nevertheless, gave ample 

 evidence of their difference in composition, owing to their actions on 

 independent substances. The experiments of Moller, Bonnier, and 

 Haysen, pupils of Elfving, show that the fvmgus in the absence of 

 algse either does not develop at all or develops badly, and that spores 

 do not develop a mycelium in the absence of gonidia. If, however, 

 gonidia are introduced to such cultures, the mycelium begins to 

 develop much better. Is not this direct evidence of the fact that the 

 vitality of the fungus has been reduced to such an extent on account 

 of its parasitic mode of life and that it has lost the power of living 

 independently ? Pure gonidial cultures separated from the thallus of 

 the lichen lead to an exactly similar conclusion. In 1867 the experi- 

 ments of Prof. Faminsen, together with those of Prof. Baranetsky of 

 the University of Kiev, showed that if a lichen is left in water the 

 fungus web becomes rotten, while the alga continues to live, grow, and 

 multiply both by fission and by zoospores. The splendidly arranged 

 experiments of Artari with pui'e cultures of gonidia from the thallus 

 of JLanilioria parietina and Oasparrinia tiniroriim show clearly that 

 the gonidia are capable of existing independently, growing on a 

 substratum containing the necessary mineral salts, but not develop- 

 ing so well as on media containing pepton and sugar. In this 

 manner the two components closely united in the symbiosis of a 

 lichen display distinctly varied characters when living independently, 

 and consequently their relations to each other cannot be such as one 

 would expect in a case of simple mutual symbiosis. The persistence 

 of the gonidia is present to such an extent in a lichen thallus that it 

 was sufficient to serve as the foundation of Elenkin's- theory of the 

 endosaprophytism of the fungus on the alga, while the facts described 

 in the present work impress one even more strongly with the passive 

 part played by the gonidia and clearly show the parasitism of the 

 fungus. There is this difference between the gonidia and free chloro- 

 cocci, that the former develop better in nourishing media containing 

 substances with complex molecules (peptones), as is shown by the 

 experiments of Artari. These circumstances can in no way be used 

 as an argument in support of the mutualistic theory. The conditions 

 of life of the gonidia competing with the fungus inside its mycelium 

 might easily react on the algae in some physiological manner, creating 

 amongst other things that power of absorbing organic food more 

 readily than of assimilating it from inorganic substances. It is 

 possible that in the thallus of the lichen the gonidia make use both of 

 the prepared peptones and of some of the organic material of the 

 fungus, and that these circumstances, relieving the gonidial cells of 

 some of their vital processes, assist them in their struggle against the 



