BULLETIN No. 219. 



COMPARATIVE STUDIES OF CERTAIX DISEASE 

 PRODUCING SPECIES OF FUSARIUM. 



Charles E. Lewis. 



The genus, Fusarium, contains a very large number of species. 

 The descriptions of many of these are very incomplete, fre- 

 quently, being based on the examination of a single collection of 

 material. Since cultural studies of certain species have shown 

 that the same fungus may show quite different characteristics 

 when the conditions for growth are changed, the validity of 

 many of the species is called in question. For example, in cer- 

 tain species of Fusarium starting with material from a colony 

 from a single spore it would be possible by growing the fungus 

 on different culture media to bring about differences as great as 

 tho?-"' which have been used in the separation of species. In 

 many cases, in those forms which are parasitic, the occurrence 

 of a Fusarium on dift'erent though closely related hosts has 

 been considered sufficient reason by certain writers for describ- 

 ing the fungus on each as a different species. A good illustra- 

 tion of this is found in the fungus causing the scab of a number 

 of cereals. It was described under a different name on each 

 host but the work of Selby and Manns * has shown that the 

 same fungus causes the disease in several hosts. This was 

 determined by growing the fungus from each host in culture, 

 comparing the cultures and making cross inoculations. 



It is probable that careful and extended cultural studies 

 together with inoculation experiments will greatly reduce the 

 number of species. One great difficulty lies in the incomplete 

 descriptions which make it impossible in many cases to deter- 



* Selby, A. D., and :\Ianns, T. F., Ohio Expt. Sta., Bui. 203, p. 231, 

 1909. 



