vit] Smuts 75 
In the case of the covered forms a large number 
of the smutted ears are harvested with the sound ones. 
On threshing the smutted grain is broken and the spores 
+f 
¥ 
¥ 
Fig. 25. Oat plants attacked by Ustilago avenae. 
are spread to the sound grain. With loose smut of 
oats the spores are blown about by the wind from the 
time that grain is ripening until harvest. A number 
of them settle on the chaff of the oat flower when it 
opens, and on harvesting these get on the grain. In 
