90 



Flag Sinnt of Wlieat. 

 Symptoms and General Characters. 



The first indications of the disease are seen on the leaves, where it forms 

 long grey streaks at first running parallel with the veins, and the black pow- 

 dery spores are set free by the rupture of the leaden-coloured epidermis. 

 The ruptured skin and long black streaks suggested a kind of rust to the farmer, 

 and so he called it " Black Rust." The ear is rarely formed, for what should 



Fig. 11. Portion of Sheath 

 showing elongated black 

 imes caused by the fungus. 



be the ear is generally only a twisted mass of diseased tissue as seen in 

 Plate IV. Occasionally the grain is formed, but it is extremely small and 

 shrivelled, and only in very exceptional oases have a few seemingly perfect 

 grains been found. On trying to germinate some of these they all died within 

 a few weeks. 



The leaves generally become curled and twisted up, and the entire plant 

 often withers before it comes into ear. All the stalks in a stool may be af- 

 fected, which is usually the case, or only a portion of them. From the way 

 in which the affected plants die down in the midst of an otherwise perfectly 

 healthy crop the true cause of the shortage in the harvest is often not realized, 

 but the curled and twisted and streaky leaves of the earless plants are sure 

 evidence of this disease. 



Effects. 



In South Australia, where the disease has lon:^ been known in the wheat 

 crops, it is regarded as being in some seasons quite as injurious as the rust 

 itself. In Victoria as much as half the crop may be lost through it, and in 

 New South Wales Dr. Cobb has shoM^i it to be equally bad. It was observed 

 in Japan that all the wheat plants in an area of about one quarter of an acre 

 were entirely destroyed by it, but this was an exceptional case. 



From the way in which some plants of a stool are affected — others not — 

 and from the fact that the disease generally prevents the formation of ears, 

 the farmer is often at a loss to know the true cause until his attention has 

 been specially called to it. He knows that his crop promised earlier in the 



