20 FUNGOID DISEASES 



The second mode of entrance Is found In those 

 fungi whose spores are disseminated by the wind, 

 e.g. the germ tube from the zoospore of Phytoph- 

 thora, If near a stoma, enters It, being attracted by 

 certain food substances — " chemotropism ". 



The third method of entrance, I.e. through some 

 wound, is the most widespread, Indeed It is highly 

 probable that many fungi which are said to enter In 

 other ways gain admission in this manner. Many 

 parasitic fungi may be placed on the surface of a 

 healthy plant, where the epidermis is intact, without 

 gaining an entrance ; but should the least abrasion 

 be made. Inoculation Is almost certain. This Is 

 well Illustrated in the pruning of large trees ; If no 

 dressing is applied to the cut surface Polyportts or 

 some other fungus usually finds an easy entrance 

 and ultimately causes decay of the parts. 



The root hairs of the plant are delicate organs, 

 and hence it seems fair to conclude that some fungi 

 enter plants through them. When other channels 

 of Infection prove uncertain a fungus Is said, either 

 rightly or wrongly, to pass in via these hairs, but 

 as before mentioned, some of the cases attributed 

 to such entrances are more or less obscure, e.g. 

 Plasmodiophora bras sices. 



N'atural Conditions Favouring the Spixad of 

 Fungoid Diseases. i. Weather Conditions. — A 

 moist atmosphere combined with warmth provides 

 the optimum conditions for fungoid development, 



