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TEXTBOOK OF BOTANY 



the Indian corn rust. In the case 6f each of these rusts, the summer 

 stage is passed upon a cereal grain, and the spring stage, where one 

 has been found, is passed upon an entirely different plant. For ex- 

 ample, the crown rust of the oat has its spring stage on the buckthorn, 

 and the spring stage of the com rust is found on the wood sorrel. 



100. Apple Rust. — The fungus that causes this disease 

 produces its winter spores upon the red cedar (juniper), 



Fig. 31. — A " cedar apple " in the spring ; the finger- 

 like projections are masses of jelly in which the winter 

 spores germinate. After Jones and Bartholomew. 



where it causes the swelhngs of the twigs and small branches 

 that are called " cedar apples " (Fig. 30). The cedar tree 

 is weakened if it is seriously affected, and sometimes it is 



