DISEASES OF CEREALS AND GRASSES 6i 



may be very badly infested before the ear appears. 

 In bad attacks the ear never gets out of the sheath. 



Cause. — The appearance of this disease is often 

 due indirectly to adverse weather conditions 

 weakening- the plant, but directly to the fungus 

 H . gramineimi, which penetrates and destroys the 

 tissues. How winter is passed over, and how in- 

 fection takes place the following spring, is not 

 known. 



Preventive Measures. — No definite means of pre- 

 vention are known. Spraying with different fungi- 

 cides has been carried out at Cambridge, but the 

 results are not very promising. 



{c) Blackening of Straiv and Black-ended Inxrlcy 

 ( Cladosporiu77t herbarM7n ) . 



Fungi hnperfecti ; Order 



With humid weather 

 conditions the straw of 

 wheat, oats, and barley 

 becomes a black or greyish 

 colour. In some cases the 

 o-rain also becomes black- 

 ened, hence the term 

 " black-ended barley " (see 

 Fig. 17); such barley being 

 considerably reduced in value. 



Cause. — With moist conditions the mycelium of 

 C/adosporiMm herbarum grows abundantly on and 

 in vegetable matter. This fungus is widespread. 



M ON I U ALES. 



Fig. 17. — Black-ended barley : 

 (A) healthy grain ; (H) black- 

 ended grain, caused by the 

 fungus Clatlosporiiiiii her- 

 bnrnm. 



