286 Frederick Stoivard : 



desirable and justifiable for a State to close its ports and 

 markets against the importation of tubers from another State, 

 in ^Ailic•h the crops furnishing the main source of seed-supply 

 have, it may be very recently, been badly invaded by Irish 

 Blight. On the one hand absolute prohibition of a particular 

 foodstuff is a difficult and grave matter ; on the other the intro- 

 duction of disease-carrying seed tubers constitutes a grave 

 menace to the local industry, especially if no previous and 

 authentic history of its appearance exists, or if such has been 

 authentically recorded, no recrudescence of the disease has mani- 

 fested itself after the lapse of a period of time which may 

 reasonably be supposed to have been ample for its complete dis- 

 appearance. 



It follows that if a means could be devised, at once not too 

 costly or difficult of execution, whereby bright-infected tubers 

 could be subjected to treatment which, while rendering them 

 useless for seed purposes, would not impair their use for human 

 consumption, then the dual menace suggested might effectively 

 be surmounted. 



The importation of blight-carrying tubers might then be per- 

 mitted without risk of introducing or re-introducing diseased 

 material, and moreover its subsequent dissemination by plant- 

 ing affected tubers might be practically if not completely 

 eliminated. 



As we have seen, although prolonged steeping of blight-free 

 tubers in aqueous solutions of sulphuric acid under certain 

 definite conditions results in (1) the complete destruction of the 

 sprouting power of the tuber, and thus renders it useless for 

 seed, it does not (2) seriously impair either its keeping or culinary 

 qualities. The experimental work briefly described in the 

 present section relates exclusively to the steeping of blight- 

 infected material, of which various lots, dift'ering in type of 

 potato and degree of infection, were obtained and subjected to 

 treatment on both a laboratory and a larger scale. 



An illustrative example will suffice. Six lots (15-20 each) of 

 tubers were separately steeped for ten days as under : — 



Experiments 1, 2, 3, 4, 5, 6 in solutions indicated in the 

 following table. 



