LECTURE XII 

 MYCOTROPHIC PHAGOCYTOSIS 



Significance of the Term: — In 1905 Bernard had arrived at 

 the conclusion that orchid "symbiosis is in some sort a serious and 

 prolonged disease, intermediate between a fatal malady and complete 

 immunity." This idea was elaborated in 1909: Bernard sought to 

 show, as VuiLLEMiN said, the common characters between infectious 

 diseases of animals and those of plants, and the narrow bonds which 

 unite the states of symbiosis and disease. He transported to botany 

 the medical terms of vaccination, immunity, phagocytosis, etc. The 

 word "phagocytosis" connotes three distinct actions, vis. (1) Attrac- 

 tion of foreign bodies, (2) their capture or active penetration in the 

 element into which they are drawn, (3) their intracellular digestion 

 and assimilation. But for Bernard the word "phagocytosis" implied 

 nothing more than intracellular digestion ; and he dissociated the 

 first two acts from the third. He regarded the Rhisoctoniae and their 

 orchids as two antagonists (1909&), developing their means of 

 attack and defense; while symbiosis {i.e., mutualism) represents an 

 immunity attained by phagocytosis. The plant makes use of all its 

 means of defense in order to preserve its essential tissues. 



After this vitalistic statement, the mechanics of the reputed de- 

 fensive action are related. The formation of mycelial coils in orchids, 

 of Gallaud's arbuscles in mycorrhizae of Allium, of Janse's spor- 

 angioles in roots of plants in Java, are all considered phenomena of 

 agglutination due to a humoral property of phagocytotic origin. But 

 Bernard did not overlook the fact that clotting of hyphae took place 

 in cultures of Rhisoctoniae where there could be nO' question of lytic 

 action induced by an orchid tissue. Bernard's untimely death put a 

 stop to these significant studies. 



It should be noted that there is a distinction between phago- 

 cytosis, which is probably a proteolysis in large part, and toxicity. 

 MacDougal & Dufrenoy (1944) neatly contrast this difference: 

 "The action of the 'humoral' secretion ... is to be distinguished from 

 toxicity by the fact that in the first case the secretion simply blocks 

 some of the processes of cell metabolism but does not destroy the 

 mechanism; in toxic action (as in pseudomycorrhizae) a theoretical 

 secretion causes irreversible and fatal changes in the cytochemical set- 



