270 



SYMBIOSIS 



and so as to " extremely determine " (devour) the other. The 

 same reservation applies to the following remark : 



Si les variations d'activite des champignons endophytes ont bien eu, 

 comme je crois, une importance essentielle pour 1'evolution des Orchidees, 

 on peut penser que 1'adaptation de ces plantes a des conditions variees 

 d 'existence a ete aussi une consequence de Faction de leurs commensaux. 



I have already expressed, in a previous chapter, the idea of 

 such determination of organism by organism. It only remains 

 to introduce a little more precision. The fungi have had some 

 importance in the (late) evolution of the orchids. Once admitted 

 as partners, they have to some extent determined the adaptations 

 of the orchids. The degree of determination depended upon the 

 degree of susceptibility shown by the orchids. The more the 

 latter became indolent in-feeders, the more they were obliged to 

 shape their adaptation in accordance with the needs, real and 

 fictitious, of their associates, and in a manner irrespective of their 

 own real good. 



The description furnished by Prof. Bernard of the penetration 

 of the orchids by the fungi rather suggests that even at the 

 eleventh hour, i.e., with intimacy so close as almost to be parlous, 

 the symptoms are yet such as to suggest a state of Symbiosis 

 rather than one of Parasitism. He speaks of " regions de passage " 

 in the orchid seedling (regions through which the fungi have leave 

 to pass in or out), attributing to them a double " privilege " 

 " elles peuvent d'une part attirer les champignons et, d'autn 

 part, elles n'opposent qu'une faible resistance a leur penetration." 

 It is admitted in fact that the orchids " attract " the fungi, 

 though, as we are told, not through a great distance. What is 

 more, we are at last reminded that at bottom some economic 

 purpose is to be served by Symbiosis, thus : "les regions de 

 passage sont precisement les regions superficielles les plus 

 permeables, ayant le role essentiel pour Tabsorption ou plus 

 generalement pour les echanges d'eau et de substances dissoutes 

 entre la plante et le milieu exterieur." 



All of which suggests a relation of neighbourly mutual exchange 

 as the original basis of the intimacy, the fungal mycelia learning 

 to increase their surface by means of clusters, which I believe, 

 gives increased scope to the operation of surface-tension 

 and thus supplies more completely the requirements of the 

 orchids. The fungal cluster would thus appear as the symbiotic 

 parallel and complement of the orchidean " region de passage," 



