ASCOMYCETES 



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the heavy soils of central Alabama were somewhat peculiarly 

 affected by this fungus. There is first a yellowing and finally- 

 a drying out of those portions of the leaves farthest from the 

 main fibrovascular bundles, that is, between the lobes. Later 

 such leaves might fall, or the whole plant might become wilted, 

 and finally brown and dead. In other regions of the country the 

 "wilting" is much more a characteristic appearance, — the dis- 

 ease being scarcely noticeable, except in a stunted condition of 

 the plants, until finally wilting results. In general, the disease 



Fig. 98. Cotton Plants of the Same Age: to the Left, Healthy; 

 to the Right, affected by Wilt. (Photograph by W. A. Orton) 



is typically that of a wilt in the case of both cowpeas and water- 

 melons. The affected plants have therefore the appearance which 

 any plant would have when deprived of its water supply, that is, 

 a general wilting and drying up. On cutting the stem, or even 

 the leaf petiole of affected cotton, a darkening of the xylem por- 

 tion of fibrovascular bundles is shown, and this is an excellent 

 indication of the presence of this fungus, since no other disease 

 now known discolors the xylem in this way. In some cases 

 plants affected and dwarfed show little or none of the characters 

 in the stem, yet an examination of the larger root branches and 

 even the tap root would show the characteristic appearance. In 



