13° 



FUNGOUS DISEASES OF PLANTS 



are the seat of action, and later the pitted vessels are infested. 

 In late stages of the disease the lesions may be considerable, the 

 bundle system being broken down and cavities formed in the ad- 

 jacent tissues. The lesions are also very noticeable when the 

 organism has gained entrance to the fruit. 



The organism is a rod averaging two or three times as long 

 as broad, 1.2-2.5 X >5--7> often adhering in twos, and rapidly 

 motile only when young (Fig. 37). The rods are readily stained 



Fig. 36. Bacterial Wilt of Melons. (Photograph by H. H. Whetzel) 



with carbol fuchsin, but the flagella are not so readily demon- 

 strated. Growth in bouillon results in a turbidity, and in potato 

 decoction viscosity is developed with age. Coagulation of milk 

 does not occur, and after weeks no viscosity is evident. On 

 gelatin growth is slow, and there is no liquefaction. Similarly, 

 on agar the clear, or milk-white, colonies spread slowly. Stab 

 cultures develop a slight growth throughout the extent of the 

 stab, with lobulated projections. On slices of potato there is a 



