262 VEGETABLE FOES AND DISEASES 



detect any trace of the disease, even in the stem of the 

 plant, for any considerable distance above ground. 

 Thus the disease appears to have degrees of virulence 

 or the plants possess varying resistive power. 



History. In all cases the root is attacked first. 

 The fungus gains entrance to the plant through the 

 rootlets, often by the radicle or tap-root, and gradually 

 extends to the root-stem. Its mycelium ascends in the 

 woody tissues of the root-stem, and presently the plant 

 begins to droop or " sleep ". If a stem is cut through 

 just above ground at this stage, drooping being well pro- 

 nounced, a brown discolouration of the woody tissues 

 or vascular bundles will be noticed clearly by the naked 

 eye, and this is a certain indication that the disease has 

 extended so far up the stem. Shortly after this the 

 cortex or bark at the junction of the stem with the 

 soil becomes brown, and presently is more or less 

 covered with a very delicate white mould. This 

 consists of the first stage of the fungus, being fruiting 

 branches or conidiophores, and bearing conidia in 

 whorls, shown at E, p. 266. This Diplocladium stage 

 of the fungus is quickly followed by the Fusarium 

 condition, which forms from the same mycelium that 

 previously produced the Diplocladium. The Fusarium 

 stage is shown at F, p. 266. Another form of fruit 

 is produced on strands of mycelium in the soil, which 

 are termed resting spores because they remain dormant 

 for a season and then germinate. These bodies are 

 shown at G, p. 266. 



The first stage spores fall to the ground when 

 mature. They germinate and produce a mycelium 



