166 RED ROT OF SUGARCANE. 



which was traced in every case to an infected adventitious rootlet 

 eye. At the 20th node there was another broken shoot, through 

 which infection had occurred. In all these cases, sections taken so 

 as to include the shoot or root and the main stem, enabled the 

 hyphae to be clearly traced from one to the other. In another case 

 infection occurred through root eyes at the 15th node and also in 

 the 8th internode through a crack in the rind. This is one of the 

 few cases where infection has been found arising from a definite 

 stem wound. The cane was also affected with smut {Ustilago 

 Sacchari). 



From the above experiments it appears that wounds caused 

 by boring insects, while undoubtedly capable of admitting the 

 parasite should it reach them, are not, in practice, responsible for 

 many cases of red rot in India. Old leaf scars are not readily pene- 

 trated, but since infection through the leaf bases has been obtained 

 by Howard, this probably depends on the degree to which abscission 

 has progressed at the time of inoculation. Under normal conditions 

 the leaf scars are not exposed until the leaf has completely withered 

 and, as our inoculations show, such scars are not readily infected. 

 During the process of wrapping, which is common in parts of India, 

 less completely withered leaves are sometimes torn away from the 

 stem, and the scars left in these cases are probably a source of 

 danger. In a few cases the cracks which form in the internodes 

 of some varieties probably admit the fungus. One such case is 

 recorded above. I^ut the commonest points of entry in new 

 infections of the above ground stem, in India, are undoubtedly 

 the shoot and root eyes at the nodes. 



The source of infection in new attacks. 



We now come to another aspect of the subject and that is the 

 source of infection in those cases in which new attacks occur in the 

 cane stem. Practically all observers are agreed on the comparative 

 rarity of the sporing stage on the surface of diseased cane stems, 

 until these have dried up more or less completely. When we con- 

 sider the extraordinarily abundant production of spores in most 



