234 



FUNGOUS DISEASES OF PLANTS 



the cotton-growing states. It has, however, been found as a most 

 serious malady in portions of South Carolina, particularly on the 

 sea islands, also in many localities of Georgia, Alabama, and 

 Louisiana. It exists also to less extent in other southern states, 

 and as far west as Arkansas. The writer has not observed it in 

 Texas, although points in all parts of the state were visited in 1 900 

 and 1901. On the watermelon the fungus has also been found 

 in much the same territory, but most abundant in Virginia and 

 South Carolina. The cowpea is affected in many southern states. 



FIG. 97. A COTTON FIELD CONTIGUOUS TO THAT IN FIG. 96, BUT PLANTED 

 TO A RESISTANT STRAIN OF COTTON. (Photograph by W. A. Orton) 



Climatic relations. The wilt diseases do not appear to be to 

 any great extent dependent upon climatic conditions. The fungus, 

 as will be shown later, is normally to be found in the soil, where 

 it may perhaps exist saprophytically for indefinite periods. Neither 

 severe temperature changes nor general differences in soil condi- 

 tions seem to be of special consequence. Plants in sandy regions 

 may be more readily wilted than those in soils more retentive of 

 moisture, but, at the same time, the fungus evidently does no 

 greater damage ultimately in one soil than in the other. 



Parts of the plant affected. The wilt disease of cotton was 

 first described as a " Frenching " (Atkinson). Cotton plants in 



