Lecture XII 



181 — 



Mycotrophic Phagocytosis 



& Fremont (1935) discovered when they applied stable manure or 

 cover crops to plots of Citrus and found that the trees seemed to 

 develop resistance to the fungus, a resistance which untreated trees 

 seemed to lack. In the treated trees they found that the cytoplasm of 

 the host-cell enveloped arbuscles of the fungus with apparent active 

 proteolysis. It is evident that with better conditions of growth the 

 Citrus trees had more H-ion at their disposal for breaking down of 

 the fungus. 



In this connection likewise may be cited the writer's (1944) 

 studies of chestnut, sprouts of American chestnut having little 

 resistance to blight whereas seedlings have decided resistance. More- 

 over, seedlings under better conditions of growth in a natural wood- 

 land are more resistant than seedlings in the open. Resistance to 

 the fungus is once again, in these observed cases, correlated with 

 vigorous growth. 



"One seems justified in concluding that the mycorrhizal fungi, both 

 ectophytic and endophytic, are potential parasites controlled by 

 reactions of the host-cells" (Burges, 1936). Lacking sufficient ioniz- 

 able substance, the tissue is parasitized and progressively destroyed. 

 Possessing requisite ions the tissue breaks down the fungus. 



