276 SYMBIOSIS 



(namely, of cluster formation) des lors les filaments, s'accroissant en tous 

 sens et plus ou moins en droite ligne, envahissaient indifferemment tous 

 les tissus. La clef du probleme de I'immunite dans la symbiose doit 

 etre dans la decouverte des conditions qui determinent la formation des 

 pelotons myceliens. 



What, again, are the conditions determining the formation 

 of clusters ? At first Prof. Bernard thought of a mechanical 

 explanation of the phenomenon, which, subsequently, however, 

 proved insufficient, and he tells us : 



Le pelotonnement est un des modes de vegetation possibles pour les 

 Rhizoctones ; il est rarement adopte par eux dans la vie libre, mais il leur 

 est au contraire continument et regulierement impose dans la symbiose. 

 Puisque la structure cellulaire des plantes n'est pas la cause mecanique 

 de cet etat des choses, on ne voit guere pour 1'expliquer que des raisons 

 physico-chimiques. II doit s'agir la d'un phenomene lie a la nature de la 

 seve intracellulaire des plantules et c'est sans doute, en definitive, grace 

 a une propriete " humorale " que les Orchidees peuvent imposer a leurs 

 hotes un mode de vegetation capable de ralentir et de regler leur envahisse- 

 ment. 



We are thus practically brought back to socio-physiological 

 causes, in particular to feeding and what is involved in biological 

 and related physiological activities. For it is clear that " physico- 

 chemical reasons," " composition of sap," " humoral properties," 

 suggest, above all, Food ; and when we find the higher plant 

 regulating or slackening the activities of the associated fungus, 

 this suggests the exercise and also the imposition of symbiotic 

 restraint, the operation of symbiotic momenta. 



As though to emphasise his chief weakness, which consists 

 in the fact of having overlooked the significance of Norm- 

 Symbiosis, Prof. Bernard remarks on the last page of the 

 " memoire," that : 



Les conditions qui peuvent se substituer a la symbiose, comme par 

 exemple un degre relativement eleve de concentration du milieu de culture, 

 sont independantes de la plante, exterieures a elle pour ainsi dire et peu 

 capables de se modifier par son action. 



As though the " autonomous " life of a plant were normally 

 one undetermined by Symbiosis ! were a life of isolation, of help- 

 lessness and of accidents ! No wonder such narrowness of view 

 leads to a misapprehension of the entire relation between fungus 

 and higher plant, and to a fatal misconstruction of the evidence 

 afforded by research, however painstaking. Contrary to Prof. 

 Bernard's opinion, it is to a large extent in the power of the 

 autonomous plant to find good equivalents for fungal help or 



