196 Scientific Proceedings, Royal Dublin Society. 



Turning now to the work of American investigators, it is necessary first 

 to recall that of Smith and Swingle 1 published in 1904. 



These authors regarded the rot of the tuber as being caused by Fusarium 

 oxysporum Schlecht, this name being taken to be a synonym of F. Solani 

 Sacc. A perusal of their account of the disease shows at once, however, that 

 their form of rot differs in several essential points from the common dry-rot 

 of the tuber, as we know it here ; and they were apparently in error in 

 supposing that the type of dry-rot described by European authors was 

 identical with that studied by them. In Smith and Swingle's form of dry- 

 rot the infection of the tuber is stated to occur normally at its heel end, 

 through the diseased rhizome ; and the subsequent decay of the tuber is 

 stated to proceed from the region of the ring of darkened vascular tissue. 



Further, Smith and Swingle's disease does not consist merely of a dry-rot 

 of the tuber, but is one in which all of the underground parts of the plants 

 may be attacked and killed, with the result that the overground portions also 

 succumb, although the mycelium of the fungus does not penetrate upwards 

 into the aerial stems. It is rather a disease of the potato plant as a whole, 

 than merely a dry-rot of the tubers. 



Some years later Manns 2 published an account of a similar disease, in 

 which the plant becomes infected at its roots, and the tubers through their 

 rhizomes. This author proved to his own satisfaction, by means of cultures, 

 that the fungus which produced the wilt of the plant was identical with that 

 which caused the subsequent rotting of the tubers during storage. He used 

 for it the name Fusarium oxysporum Schlecht, but stated at the same time 

 that he was quite aware that the name Fusarium solani was commonly used 

 for it. 



It is quite clear that Smith and Swingle, as well as Manns, concluded 

 that the storage-rot of the tubers was caused by the same fungus as that 

 which also produced the " wilt " disease of the growing plant {Fusarium 

 oxysporum Schlecht). It seems, however, that they may have been mistaken 

 in this matter. According to Wollenweber 5 the American Fusarium oxy- 

 sporum Schlecht causes the wilt of growing potato plants, but only uses the 

 xylem of the stem-end of the tubers for over-wintering, without producing a 

 rot of the parenchyma. Further, after giving a morphological diagnosis of 

 this species, this author states that it is a " vascular parasite, cause of wilt 



1 Smith, E. F. and D. B. Swingle. The Dry-rot of Potatoes due to Fusarium 

 oxysporum. Bull. 55. Bureau of Plant Industry. U.S.A. Dept. of Agric, 1904. 



2 Manns, T. P. The Fusarium Blight (Wilt) and Dry-Rot of the Potato. Bull. 229. 

 Ohio Agric. Exp. Station. Wooster, 1911, p. 299. 



3 Wollenweber, H. W. Studies on the Fusarium problem. Phytopathology, vol. iii. 

 No. 1. Feb. 1913, p. 24. 



