Action of Chemicals on PoUdo- Tubers. 285 



the conditions of time, temperature and concentration of salt 

 Of acid stated, only minute amounts of the dissolved substance 

 diffuse into and are absorbed bv the steeped tubers. 



(2) If the skins of mature intact tubers are undamaged, the 

 entry of sidphuric acid takes place exclusively via the buds or 

 " eyes " of the tubers, and the same statement applies, at least 

 during the earlier phases of the steep experiment, in reference 

 to the entry of NaCl and H.BO.,. 



(3) If the steeping in sulphuric acid is restricted within cer- 

 tain limits of time and concentration of acid, the vitality of 

 the buds or '" eyes " of the tubers is unimpaired or not greatly 

 impaired. If these limits are exceeded, the vitality of the buds 

 is effectively destroyed, without, however, seriously damaging 

 either the cooking and edible or storage qualities of the treated 

 tubers provided tliat the period of storage is not inordinately 

 prolonged, and dry and airy storage conditions are maintained. 



Blight Infested Intact Tubers. Steeps in Aqueous 

 Solutions of Various Reagents. 



The stages of the enquiry so far related lefer exclusively 

 to the treatment of blight-free tubers, the entry, mode of entry, 

 and action on the vitality of the buds of the treated tubers, 

 of certain chemical substances, under controllable conditions 

 of experiment. The accumulation of convincing and definite 

 evidence on these points, and the possible practical application 

 of the knowledge acquired, rendered it desirable to extend the 

 inquiry to the investigation of blight-infected material. 



It became, for example, a matter of special interest to in- 

 vestigate the possible influence one or other of the methods of 

 treatment essayed might exercise on the vitality of the hiber- 

 nating mycelium of the blight-inducing fungus, which, it is 

 very generally accepted, resides in the infected tuber ; this 

 latter being regarded as the chief vehicle of dissemination of 

 this difficultly combatable disease from district to district, it may 

 be from country to country. 



The question may assume a form which is not devoid of 

 economic importance. In certain circumstances it may be 



