Minnesota Plant Diseases. 303 



grains, but are not scattered immediately after ripening. They 

 are enclosed in a membrane which includes the scales around 

 the grains. Not all of the interior of the spikelet is converted 

 into spores, but plates and shreds of material remain, which are 

 not smutted. The spores are therefore held firmly together and 

 the smut is thus known as the covered barley smut. The spores 

 are black when seen in mass and have no greenish tinge. On ac- 

 count of the compactness of the smut heads, the disease does 

 not spread with very great rapidity. It is not known whether 

 the spores infect the seedling barley as in oat smut or cause in- 

 fection later, as in the corn smut. 



The hot water method and the copper sulphate steep have 

 both been recommended. The treatment used for the naked bar- 

 ley smut is said to be effective against the covered smut. The 

 formalin method would probabl)^ be of use. 



Brome smut (Ustilago bromivora Fisch.). Brome plants are 

 subject to smut attacks and the spore masses are formed in the 

 young grain. The heads of grains do not show any abnormal 

 growth. The spore mass is usually black. 



Millet smut {Ustilago crameri Korn.). A smut attacks millet 

 plants and is sometimes abundant. At flowering time, the fun- 

 gus replaces the ovaries with black masses oi the smut spores. 

 All of the heads of the attacked plants are smutted. The spores 

 germinate in the usual way, forming a small tube from which, 

 however, secondary spores are not usually, if ever, produced. 



Care should be taken to use clean seed free from smut. The 

 hot water method has been found to be an effective preventive. 



Leaf smut of rye [Urocystis occulta. (Wallr.) Rab.]. This 

 fungus attacks several cereals but is most frequent on rye. It 

 has not been reported as very frequent in this country and it is 

 probably not at all abundant in this state. It is unlike most of 

 our common smuts in many of its characters. The spores are 

 formed in elongated lines on the leaves and stem, which are at 

 first greyish but later, after the bursting of the epidermis, exhibit 

 a black powdery smut-mass underneath. The whole plant is de- 

 formed and injured. The spores are aggregated together into 

 true spore-balls. About a half-dozen spores cling together into 

 a solid mass, in which a differentiation of labor is evident. The 

 outer spores have lost their power of germinating and act as a 



