200 Scientific Proceedings, Royal Dublin Society.' 



tubers when the latter were kept at rather high temperatures, viz. from 

 27° G. to 33° C. 



In his most recent paper 1 Wollenweber mentions eight species of Fusarium 

 as being capable of rotting potato tubers. Tho four most important species in 

 this respect are stated to be : — 



(1). F. cceruleum (Lib.), 



(2). F. discolor var. sulphureum (Schlect.), 



(3). F. trichothecioid.es Wr., 



(4). F. vcntricosum App. & Wr., 



for all of them are capable of producing total destruction of tubers when 

 inoculated through artificial wounds. 



Of the other four F. orthoceras App. & Wr. is said to be the probable cause 

 of the jelly-end rot of the potato tuber ; F. rubiginosum is a wound parasite 

 on cereals, and is also found on potato tubers, where it is less active than the 

 first three species mentioned above. F. gibbosum is said to be a probable cause 

 of potato tuber-rot, but the results of infection experiments were not so 

 uniformly positive as in other species. F. subulatum is parasitic only under 

 conditions of high humidity and restricted air supply, and is less active than 

 F. cmruleum and others. 



It will be observed that unanimity between the various authors does not 

 always prevail. Our experience leads us to believe that, in studying the 

 pathogenicity of the various species of Fusaria towards the potato tuber, there 

 are certain factors which have a very considerable influence on the results 

 which may follow inoculation. These are — (1) the variety of the tuber ; 

 (2) its condition of maturity ; (3) the length of time that the fungus used for 

 inoculation has been in purely saprophytic culture, and (4) the prevailing 

 temperature and moisture conditions. In comparative tests of pathogenicity 

 these factors should as far as possible be identical. 



Finally, reference must be made to the most recent study of the various 

 species of Fusarium associated with decaying potato tubers, namely, that of 

 Sherbakoff, 2 who describes no less than sixty-one species and varieties, 

 including all those already mentioned in the present paper. This author's 

 work consists, in the main, of a description of the various species and varieties 

 of Fusarium, according to their morphological and cultural characters ; but 



1 Wollenweber, H. W. Studies on the Fusarium problem. Phytopathology, vol. hi. 

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



2 Sherbakoff, C. D. Fusaria of Potatoes. Cornell. Univ. Agric. Expt. Station. Memoir 

 No. 6. 1915. 



