198 Scientific Proceedings, Royal Dublin Society. 



Jamieson, regarded this species as being identical with the subnormal stage 

 of F. trichothecioides. But if these two species be identical, it is difficult to see 

 why one of them (F. trichothecioides) should cause a wilt of the potato plant 

 and the other one (F. tuberivorum) should not do so. 



To some extent this discrepancy may, perhaps, be regarded as explained 

 by results obtained by Link, 1 and published in a paper which reached us 

 whilst the present paper was in preparation for press. Link states that he 

 agrees that F. tuberivorum Wilcox and Link is the same species as 

 F. trichothecioides Woll. Contrary to what was stated in his previous paper, 

 he now states that this species is capable of producing a wilt of the potato 

 plant as well as a rot of the tuber, and further he shows that, contrary to 

 Wollenweber's opinion, F. oxysporum is not only a wilt-producing organism, 

 but does also cause a rot in tubers. In other words, both F. oxysporum and 

 F. trichothecioides can produce both tuber-rot and wilt of the potato plant ; 

 but, according to Link, under field and storage conditions respectively, the 

 former is more probably responsible for wilt, and the latter for tuber- 

 rotting. 



Pratt 2 describes the rot due to F. trichotJiecioides as a " powdery dry-rot," 

 and states that it is apparently restricted to the arid and semi-arid sections 

 of the western part of the United States. He agrees that F. tuberivorum is 

 identical with F. trichothecioides, but, working with this fungus under western 

 field and laboratory conditions, he states that he failed to produce an 

 infection in any part of a growing potato plant. His results, therefore, are 

 contrary to those of Jamieson and Wollenweber, agree with those of Wilcox, 

 Link, and Pool, but differ from those of Link subsequently published. 



Two further types of dry-rot have been described in America by Carpenter. 3 

 One, called a "stem-end and wound-invading dry-rot," was found to be caused 

 by a new species of Fusarium for which the name F. eumartii was proposed. 

 The second, similar in type to the first, is caused by F. radicicola Wollenw. 

 This author refers to the so-called " jelly-end" rot, which, he says, is a serious 

 trouble in California, and he finds F. radicicola and F. oxysporum associated 

 with it. Carpenter agrees with Smith and Swingle (and with Link), but 

 differs from Wollenweber in ascribing to F. oxysporum the power of causing 

 tuber-rot. F. hyperoxysporum Woollenw. was also proved to be capable of 

 producing a tuber-rot. 



1 Link, G. K. K. A. physiological study of two strains of Fusarium in their causal 

 relation to tuber-rot and wilt of potato. Bot. Gaz. lxii. No. 3. 1916, p. 169. 



2 Pratt, O. A. Control of the Powdery Dry-Rot of Potatoes caused by Fusarium 

 trichothecioides. Jour. Agric. Research, vol. vi. No. 21. 1916, p. 817. 



3 Carpenter, C. W. Some potato tuber-rots caused by species of Fusarium. Jomrn. 

 Agric. Research, v. No. 5. 1915, p. 183. 



