2i 4 VEGETABLE FOES AND DISEASES 



moisture and temperature. These move about by 

 means of thread-like appendages or cilia, and pro- 

 bably at first lead a saprophytic mode of life, living 

 upon organic matter in a state of decay or in solution 

 of rain water. After a time two or more of these 

 bodies unite together, then form plasmodia growths, 

 either in the soil or in the host-plant, entering this 

 by the root-hairs or through the cuticle. Once inside 

 a living cell the parasite forms a mass of protoplasm, 

 which increases and passes from one cell to another 

 devouring their contents. After vegetating for some 

 time and causing the infected cells to increase in size 

 and produce the swellings known as " club-root," the 

 plasmodium differentiates, and ultimately becomes re- 

 solved into many minute round spores, which on the 

 decay of the root are liberated in the soil. When 

 the spores are set free they probably germinate, and 

 form a plasmodium that exists as a saprophyte ready 

 to seize upon any plant root affording the essential 

 food, or remain quiescent and awake to active life in 

 the presence of a peculiar host-plant. On these points 

 nothing is known with certainty, though if Cabbage, 

 Turnips, or other allied plants are sown or planted in 

 soil on which diseased plants have been produced in 

 the previous season, or even two or three years pre- 

 viously, such plants will become diseased also. 



Prevention. From the nature of this infection 

 remedial measures can have only a palliative effect. 

 It would, however, be desirable to apply a good dress- 

 ing of lime when the first symptoms of the infection 



