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STRUCTURE AND LIFE HISTORIES 



These diseases are caused by fungi of the genus Ustilago. 1 

 The species are often named from the plant affected, 

 for example Ustilago Avence on oats (Avena, Fig. 220), 



FIG. 220. Panicles of oats (Avena saliva), with the grains almost com- 

 pletely destroyed and replaced by the oat smut (Ustilago Avence). 



Ustilago Tritici on barley (Triticum), Ustilago Ze& on 

 corn (Zea, Fig. 221). The mycelium extends through the 



1 A Hemibasidiomycete. 



