xvi STOEY OF EUST IN WHEAT 



fungus plant is ready to form spores anew. These 

 spores burst through the skin of the stem or leaf, 

 and are carried by the wind to other wheat plants, 

 which are thus infected in their turn. 



This goes on all through the summer weather, 

 but autumn comes on, and the wheat plants begin 

 to turn yellow. This is a warning to the fungus 

 that it is time to prepare for winter. It stops 

 producing the rust-coloured summer spores, and 

 instead produces dark-coloured resting spores (the 

 mildew), which have a thick coat to resist the 

 winter cold. 



These dark-coloured spores remain through the 

 winter in what is called a resting condition. When 

 spring comes they sprout on the ground and make 

 new spores. But where can these go ? The wheat 

 is very little above the ground ; it cannot yet feed 

 a greedy fungus. But in the hedgerows the bar- 

 berry bushes are putting out their fresh leaves. If 

 the spores are by chance carried to these leaves, 

 they again sprout and form pretty little yellow 

 cups on the under side of the leaf, each cup being 

 full of spores. These spores are carried later by 

 the wind to the wheat, and so the whole story 

 begins over again. 



This, then, is the history of rust, as it was 

 finally worked out by de Bary. It might be said 

 that it shows that the way to stop rust is to root 



