100 C. D. Sherbakoff 



mial nor typical pionnotal form of fructification was observed in any of 

 the true Fusaria, though types of fructification resembling those forms 

 more or less closely were common. 



SCOPE OF WORK 



The work was confined to a study of the Fusaria as such, that is, without 

 any consideration of the possible perfect forms. 3 The study was centered 

 mainly on the characters that seem to be most important and practicable 

 for a natural classification of these organisms. Thus, especial attention 

 was paid to the presence and type of each kind of spores (micro- and 

 macroconidia and chlamydospores) . Type of color production was found 

 to be next in importance. Type of fructification and of conidiophores, 

 size of spores, presence or absence and kind of sclerotia, and rate and 

 character of colony growth, were also found to be of more or less consider- 

 able importance for differentiation of the species. 



Some work has been done on the action of these organisms under 

 different environmental conditions and also with respect to their patho- 

 genicity. In regard to the latter the following four facts should be men- 

 tioned : 



1. Extensive inoculations of potato plants with all the Fusaria pre- 

 sented here yielded negative results and would indicate that they are not 

 wilt producers. 4 



2. Several series of inoculations of potato tubers showed (a) that a con- 

 siderable number of the Fusaria can cause more or less rapid decay of the 

 tubers, and (b) that most of the Fusaria readily produce rot only after the 

 tubers begin to sprout. 



3. The commonest rot-producing organism, at least in eastern United 

 States, is F. coeruleum (Lib.) Sacc. 



4. The inoculations into tubers seem to indicate that some species 

 widely different morphologically may act similarly pathologically, and 

 that other species very closely related from the morphological standpoint 

 differ very widely in their pathogenicity. 



The other results of this phase of the work will be mentioned only in 



3 In this study no special attempt was made to discover the perfect stage of any of these organisms. 

 At the same time it is to be noted that under the condition of the work when a considerable number of 

 " natural " as well as " artificial " media were used, none of the Fusaria produced a perfect stage. 



4 The writer does not mean by this statement that the Fusaria actually never produce wilt of potatoes, 

 because it is possible that the negative results were due to lost virulence of the cultures used or to some 

 other important factor that escaped attention. 



