Plant Diseases 
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sticking; out of them. If these hair-like structures are 
examined under a microscope, they will be found to consist 
of little stalks bearing branches, which in turn bear very 
minute oval bodies or spores. These spores do not give 
rise directly to the disease plant. They divide into a 
number of smaller spores, which are able to swim about 
in the smallest particle of moisture by means of two cilia. 
The slightest quantity of dew is sufficient for these 
Hyphae of Parasitic Fungi 
zoospores, as they are called. In this moisture they ger- 
minate, and so give rise to the disease plant. The little 
thread-like structures already spoken of are the fruiting 
branches or conidiophores of the disease plant. The plant 
itself is inside the Potato leaf, and is made up of a mass 
of hyphse or little tubes, which is called the mycelium. 
When the mycelium has made considerable growth, it 
begins to send out fruiting branches. These make their 
way to the stomata on the leaves, and grow out through 
them into the atmosphere, and there form the spores. 
While the fruiting branches or conidiophores are being 
