288 Frederick Stoioard : 



The evidence derived from these experiments indicates that 

 when mature blight-infected tubers are steeped under the above 

 conditions, examination of the material at four or ten days fails 

 to reveal its presence. The evidence was just as conclusively 

 negative in experiments 1-6 as it was positive in experiments 

 7 and 8, and it is ditiicult to interpret the results other than 

 by stating that as the result of steeping infected tubers in both 

 solutions (experiments 1-5), or in plain water (experiment 6) 

 the hibernating mycelium of the fungus is completely sup- 

 pressed. In the latter, it is not improbable, considering the 

 marked aerobism of the fungi in general, that the effect is 

 induced by asphyxiation through prolonged drowning. 



Planting tests carried out with portions of the material from 

 experiments 1 to 5, were entirely negative, while the material 

 from experiment 6 underwent advanced decay, during the pro- 

 cess of steeping. 



Subsequent work in this direction was confined to steeping 

 blight-intected material in aqueous solutions of 2.5, 5.0, or 10 per 

 cent, strengths, for a uniform period of steeping of 16, and 

 finally of 10 hours' duration. Different kinds of tubers varying 

 considerably in degree and extent of infection, were used, and 

 the magnitude of these latter experiments enjerged from a 

 laboratory to a practical scale, a sack (1^ cwt.) of tubers being 

 steeped in each of these essays. The customaiy "forcing," storage 

 and cooking tests were carried out in each of these experiments. 



While a steep of 10 hours' duration in a 2.5 or 5.0 acid 

 generally proved inadequate to suppress the vitality of buds 

 and fungus, the results of steeping material for the same period 

 in 10 per cent, acid were invariably negative, i.e., no develop- 

 ment or growth of either buds or fungus ensued. The most 

 careful microscopical examination failed to reveal the presence 

 of the fungus ; contemporaneous " forced " controls invariably 

 gave positive results. 



These results justify the conclusion that when blight-infected 

 mature tubers are steeped in 10 per cent, aqueous sulphuric acid 

 for 10 hours, the sprouting power of the steeped tuber and the 

 hibernating mycelia of the blight fungus were completely 

 destroyed. 



