190 TILLEES OF THE GEOUND CHAP. 

 CHAPTEE XVI 



THE STORY OF RUST IN WHEAT 



How can we recognise the disease variously known 

 as blight, rust, and mildew ? Suppose we examine 

 in summer-time a field of wheat, oats, 'or rye, or 

 even a meadow full of grass. Especially if the 

 summer has been a damp one, we shall find quite 

 likely that some of the plants have long, rusty- 

 brown streaks on the stems and leaves. These 

 streaks are like rust not only in colour but also in 

 the fact that we can rub off a red powder. Later 

 in the season we may find, instead of these rusty 

 streaks, black or very dark streaks, which blacken 

 the fingers, just as the other kind reddened them. 

 The first stage is the rust stage and the second the 

 mildew stage of wheat disease. (See the diagrams 

 on p. 198). 



The next point to be considered is, what harm 

 does the rust or mildew do to the wheat plant ? 

 This is very readily explained. The black or 

 brown streaks on the leaves mean that the substance 

 of the leaf is largely destroyed. Now it is by the 

 leaves that the plant makes the starch which so 

 largely fills the grain. The presence of the streaks 



