Pethybiudge and Lafferty — Dry -Rot of the Potato Tuber. 201 



a certain amount of attention is also devoted to the question of the patho- 

 genicity of the different species towards the potato. Inoculations of potato 

 plants with all of the species described gave negative results as far as wilt 

 production was concerned, but the author does not conclude that all of these 

 species are incapable of producing wilt, given the proper conditions. Inocula- 

 tions of tubers showed that a considerable number of the species caused more 

 or less rapid decay, and that most of them only readily caused rotting after the 

 tubers had begun to sprout. The commonest rot-producing organism, at least 

 in the eastern United States, is said to be F. cceruleum (Lib.) Sacc. 



It is stated 1 that this organism was isolated repeatedly from diseased 

 tubers, and every strain isolated proved capable of producing more or less 

 dark-coloured dry-rot in tubers. Further, Sherbakoff states that a white- 

 rot of tubers is produced by F. lutulatum and some of its allies, a distinctly 

 striate rot by F. striatum, a brownish rot by F. trichothecioides, and a more or 

 less pinkish rot with large cavities by F. suhulatum and its variety brevius. 

 Of all these F. cceruleum is stated to be the commonest and most vigorous 

 wound parasite of potato tubers, the next perhaps being F. suhulatum, and its 

 variety brevius. 



It is apparent from a review of the literature that the potato tuber is 

 capable of being destroyed by several totally distinct species of Fusarium, 

 and that in most cases the decay is of the nature of a dry-rot. It is also clear 

 that some of these species may produce a " wilt " of the potato plant. Our 

 object was therefore to find out whether one or more of these species, and 

 if so which of them, was responsible for our common dry-rot, and to ascertain 

 whether the species concerned also caused a wilt-disease of the plant. 



III.— Investigation Woek. 



The investigations dealt with in the present paper have been in progress, 

 concurrently with studies of other potato diseases, during the past three or 

 four years. 



Naturally, much of the diseased material examined has been of Irish 

 origin, but we have also been fortunate in securing for detailed investigation 

 a number of characteristic specimens of the disease from England and 

 Scotland 2 sufficient to lead us to believe that there is but one commonly 

 occurring form of dry-rot affecting potato tubers in the British Isles. 



1 loc. cit. p. 261. 



2 We desire to express our thanks to Mr. A. D. Cotton, of Kew ; to Mr. E. S. Salmon, 

 of Wye ; and to Dr. W. G. Smith, of Edinburgh, for their kindness in providing 

 us from time to time with supplies of typically diseased material from England and 

 Scotland. 



o IT 

 SCIENT. PROC. E.D.S., VOL. XV., NO. XXI. - «■ 



