MALADIE ET SYMBIOSE 267 



physiologiques " vis-d-vis to the orchids, namely, when, as is 

 often the case in greenhouses, the fungi succumb to the temptation 

 of living " en saprophytes " (as unrestrained in-feeders), Prof. 

 Bernard has some observations with regard to the prevention of 

 disease in cultivated orchids, which remarks generally apply in 

 the case of prevention. This is what he has to say : 



Des pratiques de culture rnal comprises peuvent avcir pour effet de 

 selectionner ces races inactives au detriment de celles dont Factivit6 se 

 maintient par la symbiose. 



In other words, we must aim at providing conditions of 

 symbiotic moderation ; and if we wish to be truly successful 

 in Horti- as in Agri- or " Physi-" culture, we must side with 

 the good and strenuous (cross-feeding) rather than the bad 

 and indolent (in-feeding) micro-organisms. More pertinently 

 still, we are told : 



La pratique des rempotages peut ainsi devenir nefaste, or elle est fort 

 en usage dans les serres soigneusement tenues ou Ton se preoccupe de 

 cultiver les Orchidees dans un compost sain, toujours recouvert de Sphag- 

 num vivant et frais. On adjoint d'ailleurs a cette pratique des soins divers 

 de proprete et de disinfection qui ont un role utile pour la defense des 

 plantes contre leurs parasites accidentels, mais qui peuvent eventuellement 

 aussi nuire a une existence reguliere de leurs commensaux habituels. 

 Des precautions trop attentives pour la culture des plantes adultes peuvent 

 devenir nuisibles pour la reussite des semis. II est bien connu en fait que 

 les semeurs les plus heureux ne sont pas toujours ceux qui tiennent leurs 

 serres avec le plus de soin. 



In the place of a reduction of the in-feeding, we supply " cures," 

 many of which, as I have been at some pains to show in Symbio- 

 genesis, are worse than the disease. I have insisted that in order 

 to understand the requirements of an organism, or to determine 

 a " standard-metabolism," we must first make allowance for 

 the needs, real or fictitious, symbiotic or parasitic, of the 

 associated organisms, and this is seen to be corroborated by 

 Prof. Bernard's experiences. 



Seeing that the symbiotic association acts as a great stimulant 

 of fungal activity, Prof. Bernard speaks of an " exaltation de 

 1'activite des champignons par la symbiose " ; but instead of 

 regarding the phenomenon as a healthy development, he compares 

 it to " la virulence des micro-organismes pathogenes," stating 

 in fact that " le degre d'activite d'un Rhizoctone, comme le degre* 

 de virulence d'une bacterie pathogene, revelent sans doute, sous 



