FUNGI 



389 



The surprising 

 thing about early 

 spring spores is that 

 usually they do not 

 attack wheat ; they 

 attack other plants. 

 It was in England 

 that the life history 

 of wheat rust was 

 discovered, and 

 there it was found 

 that these early 



Fig. 188. — The winter spores 

 of wheat rust germinating. 

 Note the short filaments at 

 whose ends short branches 

 appear bearing the early 

 spring spores. 



Fig. 187. — A, summer spores of wheat rust. B, win- 

 ter spores of wheat rust. 



spring spores germinate on the leaves 

 of barberry. The barberry is a com- 

 mon shrub. It was thought that if 

 the barberry was destroyed, the wheat 

 rust would disappear. But it was 

 found that these early spring spores 

 could germinate on other plants as 

 well as on barberry. Soon after these 

 early spring spores have produced a 

 mycelium in the tissues of whatever 

 leaf it is they attack, reddish patches 

 appear at the surface of the leaf. 

 These reddish patches form what are 

 called cluster cups. In them are found 

 the fourth kind of spore, the late 

 spring spore. (See Figure i8g.) It 

 is this fourth kind of spore which 

 germinates on the young wheat plants, 

 thus completing the life cycle of this 

 remarkable plant. 



