Family Gramineae 253 



enced when the disease attacks the ear, destroying or 

 rendering it useless for market purposes. 



Symptoms. Com smut does not usually make its 

 appearance before the plants are about three or 

 four feet high. It is manifested as boils which 

 may attack any part of the leaves (fig. 45 c), stalks, 

 tassels, or ears. The boils are whitish to glossy, 

 then purple, finally rupturing and liberating a black 

 powdery mass of the spores (chlamydospdres) of the 

 fungus. 



The Organism. Within the tissue of the affected 

 host the smut myceUum consists of short slender 

 branched filaments closely interwoven. These 

 slender filaments swell, gelatinize, and portions of 

 them round off as spores. The latter retain their 

 vitality for more than one year. The chlamydo- 

 spores (fig. 45 d) germinate by sending out a tube 

 which in turn bears true conidia (fig. 45 e, f). The 

 latter germinate by sending out a tube which pene- 

 trates the host. 



Control. Com smut is not carried with the seed 

 as is the case with oat or wheat smut. Seed treat- 

 ment in this case will therefore be useless. The dis- 

 ease is carried with the manure or in the soil. The 

 best remedy, therefore, is to cut out and destroy by 

 fire all smut boils as they appear. This must be 

 done before the boUs are ruptured. If this is care- 

 fully practiced by everyone in each community com 

 smut wiU soon disappear. Smutted ears or stover 

 should never be fed to animals, as this is a common 

 way of infecting the manure pile. 



