W. F. Bewlby 121 



were therefore arranged in which seedhngs grown under sterile conditions 

 were inoculated. Tomato seeds were sterilised in mercuric chloride, 

 washed in sterile water and germinated on agar in petri-dishes, after 

 which they were transferred to 1000 c.c. Erlenmeyer flasks in which 

 200 c.c. Czapek's agar with 1 per cent, saccharose had been allowed to 

 set. The seedhngs were allowed five days in which to establish themselves 

 in the flasks and then the medium was inoculated with a pure culture 

 of Verticillium. The fungus readily attacked the young roots, which it 

 penetrated and passing into the wood caused the seedhngs to wilt, on 

 an average nine days after inoculation. Sterile untreated controls were 

 quite healthy after 20 days. From this it seems justifiable to assume that 

 Verticillium albo-atrum can infect healthy tomato plants in the absence 

 of wounds. 



7. Fusarium inoculations. 



Four species isolated from wilted tomatoes were tested, namely, 

 F. lycopersici, F. oxysporum, F. ferruginosum and F. sclerotioides. 

 Inoculations were performed upon plants six weeks old of the varieties 

 Comet, Kondine Red, Fillbasket and Ailsa Craig. Plants in different 

 conditions of health and under various conditions of temperature, 

 humidity and hght were inoculated. F . ferruginosum and F. sclerotioides 

 never produced wilt under any circumstances and must be regarded as 

 saprophytes. The strains of F. oxysporum destroyed the pith and cortical 

 tissues round the point of inoculation and in some cases worked into 

 the roots, destroying the tissues as they went. In a few cases, at an 

 average temperature of 27-8° C.-28-9° C. a shght desiccation of the lower 

 pair of leaves was observed, but generally no wilt or desiccation resulted 

 from inoculation with this species. F. lycopersici readily produced a wilt 

 and desiccation at temperatures of 28° C.-29° C, but when the tempera- 

 ture was below this, infection was uncertain. 



' 3. Pathological Physiology. 



The pathological symptoms in the anatomy of plants suffering from 

 Wilt Disease, whether caused by F. albo-atrum or species of Fusarium, 

 are limited to a brown discoloration of the wood vessels, and the presence 

 of fungal hyphae within them. Early writers decided that the wilting 

 or premature death by desiccation was due to the choking of the wood 

 vessels with fungal hyphae and Pethybridge (16) suggested the term 

 " Hadromycosis " for these symptoms instead of the older term "Vas- 

 cularmycosis." 



