220 Scientific Proceedings, Royal Dublin Society. 



whether it or Phytophthora infestcms was the more responsible for the decay 

 of the tuber on which it was found. It certainly is not the cause of our 

 common dry-rot, but the possibility that it may occasionally be a cause of 

 dry-rot must not be overlooked. 



IV. — Conclusion. 



The dry-rot of the potato tuber which commonly occurs in the British 

 Isles is due to the attacks of Fusarium cceruleum (Lib.) Sacc. The two 

 species, F. oxysporum Schlecht. and F, trichothecioid.es Woll., which are 

 largely responsible for a somewhat similar type of rot in certain parts of the 

 United States of America, have not been met with in this connexion up to 

 the present in the British Isles. 



On a single occasion F. arthrosporioides Sherb. was met with and was 

 proved to be capable of causing a dry-rot of the potato tuber. Further 

 research may perhaps show that this and possibly some other species of 

 Fusarium are occasionally responsible for the production of dry-rot here. 



F. cceruleum does not produce hadromycosis of the potato plant, nor does 

 it kill the plant by attacking the roots. It can destroy tomato fruits, but 

 does not attack onions, mangels, carrots, parsnips, or apples. 



Infection frequently occurs through mechanical wounds such as those 

 caused by implements, by bruising, and by breaking off the sprouts. It may 

 also occur through scab spots. Wounds, however, are not essential, for infec- 

 tion can take place through the lenticels, eyes, or young sprouts of uninjured 

 tubers. 



Potatoes become more susceptible to infection as they become more 

 mature, hence the rot is more prevalent during the later than during the 

 earlier period of storage. Some varieties of potatoes are more resistant to 

 infection than others. 



Affected tubers cannot be cured, and the application of sulphur or lime 

 for preventing infection or retarding the rot is of no practical value. 



