Disease Symptoms 



to its own ends what was intended for the nourish- 

 ment of its host. Curiously contorted growths are 

 often produced through the check to the development 

 of local parts induced by the parasite, or through 

 a curious effect such as is seen in cabbage roots 

 attacked by the club-root organism, where much 

 more extensive growths than usual are induced. 

 These dead spots, contortions, and swellings afford 

 symptoms by which diseases may be recognised, and 

 will be referred to again. 



When the mycehum of the parasite is internal, 

 as a rule a number of threads are thrust out of the 

 host to form spores for the distribution of the fungus, 

 or fruits containing the spores are produced on the 

 surface of the host. The spore-bearing threads or 

 fruits are usually massed in sufficient numbers, and 

 have some characteristic colour, which enables a 

 gardener, with the aid of a pocket-lens such as aU 

 good gardeners carry, to use them for the recognition 

 of a disease. 



To make out the structure of the spores them- 

 selves, and to identify the fungus with certainty, 

 requires the aid of a compound microscope and 

 considerable training, and are usually impossible 

 for the gardener. These things are necessary to the 

 proper imderstanding of the disease, but many 

 common attacks may be recognised readily without 

 this kind of examination. 



Some fungus attacks are confined wholly or 

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