DISEASES CAUSED BY FUNGI. 



BY GEORGE MASSEE, V.M.H., F.L.S., 



Principal of Cryptogamic Department and Plant Pathologist, 

 Kew Herbarium. 



GENERAL REMARKS. 



" Prevention is better than cure " should be borne 

 in mind in all attempts to check diseases caused by 

 fungi. The reason for this is the fact that the majority 

 of fungus parasites, immediately after infection, spread 

 in the living tissues of the plant they have attacked, 

 hence it is impossible to kill the fungus without at the 

 same time killing or severely injuring the plant. As a 

 rule the appearance of mildew or other fungus on a 

 plant is considered as evidence of the primary attack of 

 the parasite. The statement that plants that were 

 healthy yesterday are suffering from disease to-day is 

 frequently made, nevertheless it is a mistaken idea. 

 When a fungus spore falls on a leaf, germinates, and 

 passes into the interior of the leaf, it commences to form 

 spawn or mycelium, which grows at the expense of the 

 materials accumulated by the plant for its own use. 

 This process of growth on the part of the spawn 

 extends over a variable period of time, depending on the 

 particular kind of fungus, but usually lasts from one to 

 two weeks, before the leaf shows any signs of the 

 presence of the parasite. When the spawn has 

 accumulated a sufficient amount of reserve food its 

 presence is indicated by a yellow or brown patch on the 

 surface of the leaf, and at a later period the fruit of the 

 fungus bursts through to the surface, when the spores 



