Fungi 



417 



germinate there, producing the 

 basidia and basidiospores which 

 are blown about and infect the 

 new crop of corn. The infected 

 region of the corn plant usually 

 swells, forming a large, glistening 

 white ball. This later turns black 

 and disintegrates, liberating myr- 

 iads of spores to be further scat- 

 tered by the wind. When the 

 soil in a field becomes greatly 

 infected with corn-smut spores, 

 the best way to avoid further 

 trouble is to plant another kind 

 of crop for a year or two. Seed 

 treatment is of no value. 



The rusts. Among the most 

 serious diseases affecting wheat, 

 rye, barley, and oats are those 

 produced by the fungi known as 

 the rusts. These fungi are called 

 rusts because plants that are in- 

 fected with them develop yellow 

 and brown spots that have the 

 appearance of iron rust. The 

 rusts occur wherever grains are 

 grown, and they cause millions 

 of dollars' worth of damage to 

 crops every year. 



The rusts are parasites that 

 live inside the host plants and in- 

 jure or destroy the tissues that 

 are concerned in food manufac- 

 ture. Their life history is pe- 

 culiar in that the fungus usually 



Office of Cereal Investigations, U. S.D.A. 



Fig. 258. Corn smut. The large white 

 masses of tissue protruding from the stem 

 contain the black spores. The mycelium 

 of this smut does not extend far from the 

 point of infection. 



