58 FUNGOID DISEASES 



rounded by an ochre-coloured collar, or muff-like 

 growth, consisting of a felt of fungus hyphae. 

 These hyphae penetrate the sheath and stem, 

 filling up the spaces between the two. The part 

 is quite hard when cut through. 



Cause. — The collar-like growth is caused by the 

 fungus Epichloe typhina, the hyphae of which en- 

 circle and penetrate the sheath and stem. The 

 colour of the collar darkens with age. 



Preventive Measures. — Very difficult to combat, 

 little beyond cutting down and destroying attacked 

 oTass can be recommended. 



VI. Wheat and Grass Mildew [Erysiphe 

 gramims). Class : x\scomvcete.« ; Order : Peri- 



SPORIALES. 



Wheat suffers to a larger extent than grasses. 



Symptoms. — During the summer months die 

 leaves of grasses and wheat become covered with 

 greyish-brown, irregular, felt-like patches on the 

 upper surface, consisting of the mycelium of the 

 fungus Erysiphe graminis. Short hyphee arise, 

 bearing conidia in chains (see Fig. i6, C). 



Cause. — The cause of the peculiar grey covering 

 is the presence of the mycelium of Erysiphe. The 

 oval spores are readily carried in the atmosphere 

 to the surface of the leaves of healthy plants, where 

 they germinate and set up new^ centres of infection. 



In autumn small dark-coloured bodies, visible to 

 the naked eye, appear on the same threads that 



