128 



'' Sleep ji Disease'' of the Toutafo 



plants in the unshaded tomato house readily wilted, those in the shaded 

 house exhibited only slight wilting. Observations in commercial glass- 

 houses have shown that temperatures between 15-6° C. and 24-0° C. 

 with an optimum of 21-1 to 22-8° C. are favourable to the rapid progress 

 of Verticillium wilt. Below 15-6° C. and above 24-0° C. this is exceedingly 

 slow, while suitable shading partially counteracts the effect of low 

 temperatures. 



A series of experiments was next arranged, in which wilted plants 

 were transferred to conditions of high temperatures to ascertain if they 

 Avould recover and if such recovery would continue, when the plants 

 were returned to lower temperatures. The results are tabulated below. 



The results in Table VI indicate that wilted plants recover when the 

 average temperature is raised to 25° C. When such a temperature is 

 operative for a short time, the effect is not a lasting one, for the plants 

 rapidly wilt again when the temperature is lowered. Longer exposures 

 to the higher temperature produce a more lasting result, for after 75 days 

 at 25° C. the plants remained turgid for 30 days at a temperature favour- 

 able to wilt. In Table VII the percentage of wilted plants, which recover 

 when transferred to a shaded house at an average temperature of 25° C, 

 is compared with that of similar plants transferred to an unshaded house 

 at the same temperature. Plants in different stages of wilt were used. 



