51 8 Journal of Agricultural Research vol. xx, no. 7 



base of the stalk when the disease was well established. The fungus is 

 said to lose its virulence in culture after the "first generation." The 

 conidia are described as straight or slightly curved, round obtuse at both 

 extremities, possessing usually three septa, their size varying from 25 to 

 35 microns by 4 to 6 microns. 



Delacroix's Fusarium disease is probably not a true wilt disease, since 

 it is not described as such. The description and illustration of the 

 causal organism are, furthermore, too fragmentary and unsatisfactory to 

 permit of comparison. The new species created (Fusarium iabacivorum 

 Delac.) has apparently not been credited by any recent workers with the 

 Fusaria. It is interesting to note that Delacroix knew of McKenney's 

 Fusarium disease but could not say whether his disease was identical 

 with it or not. In view of the fact that Delacroix's description may fit 

 other diseases of tobacco as far as symptoms are concerned, and since we 

 have only the statement that infection has been secured with an organism 

 of such universal occurrence as Fusarium, together with the unreliable 

 description of the causal organism, it is difficult to see how at the present 

 time we can accept either the disease as such or the species described 

 as authentic. 



A brief abstract was published by the writer in 1918 (4) calling atten- 

 tion to the wilt disease in Maryland and giving reasons for believing it 

 was due to Fusarium, although artificial infection had not been secured 

 at that time. 



SYMPTOMS OF THE DISEASE 



The symptoms of the disease may first become evident upon very 

 young or on nearly mature plants. Under the field conditions observed 

 it is evident that plants may succumb at any stage in their growth, al- 

 though it is not clear as to what time the original infection of the plant 

 occurs. It seems probable that infection may take place at any time, 

 but that it is more likely to occur when the plants are young, the parasite 

 remaining in a more or less latent stage until favorable environmental 

 conditions for the further development of disease occur. In full-grown 

 plants the earliest symptoms seem to be the sudden wilting of only one 

 or more leaves on the plant, accompanied by yellowing and finally brown- 

 ing and death, but not decay of the leaf. In some cases this symptom 

 at first may be localized on only one side of the leaf. At other times all 

 the leaves in a narrow vertical band, comprising about one-fourth or one- 

 eighth of the leaves of the plant, may become wilted while the others 

 remain apparently free from the disease (Pi. 64, A). If the stalks of 

 such plants are cut, it will be found that the discolored bundles are con- 

 fined to only a part of the circumference of the vascular ring. All de- 

 grees of wilting from those described, to complete collapse of all the 

 leaves on the plant, however, may occur (Pi. 64, B). If the plants are 

 pulled up, large or small dead roots may be found, while others are appar- 



