Fusarium in Tuber Rot and Wilt of PotaU 



19 



the whole plant took place, the fundus girdled the whole stem, 

 while plants that were nol girdled lived on, even though one side 

 was entirely destroyed. There was little lateral and subsequent 

 vertical spreading- of the fungus from one vascular strand to the 

 other. These experiments were repeated with 25 other plants and 

 in must cases the same symptoms were observed. These symptoms 

 have been repeatedly observed in the dry land areas of Nebraska, 



A 



B 



Fig. 5. — Rosette produced in laboratory with Fusarium oxysporum, and 

 control plant: A. control. Early Ohio variety; S, rosetted plant. tO days 

 after inoculation, Early Ohio variety. 



lmt have always been looked upon as cases id" "sun scald," and 

 in previous experiment-- with wilting due ti i F. trichothecioides such 

 cases were ignored. 



Plants grown in soil infected with F. oxysporum and F. tricho- 

 thecioides showed severe lesions of roots and stolons. Examination 

 of roots affected with either organism showed that the cortical 

 regions are first and most severely attacked, not only intercellu- 

 larly, but also intracellular!}, the cells being packed full with hvphae. 

 In most eases the cortex could be sloughed oft' with exceeding ease. 

 From the cortex the organisms invaded the stelar regions, where 



