l82 MYCOLOGY 



the maturity of the spores at the time the wheat, or barley, come into 

 bloom. This mode of infection is known as flower infection. A third 

 method is shown by the corn smut which may infect its host at any 

 time by entering the young and tender parts of the plant. A knowledge 

 of these facts is important, for the treatment of seeds will be efl&cacious 

 with smuts, which infect seeds, while it would be useless with infection 

 accomplished by the second and third methods. 



Grain smuts cause a considerable loss to the farmer every year. 

 Oat smut, it has been estimated, causes a loss of $10,000,000 per annum 

 in the United States. Smut explosions have been recorded recently.^ 

 In the wheat-growing regions of the Pacific Northwest in the summer of 

 1914, 300 threshing machines were blown up or burned by smut ex- 

 plosions. Passing into the cylinder of the threshing machine, the smut 

 balls were broken up and the highly combustible smut dust oily and 

 dry filled the. interior of the separator. It is when this condition ob- 

 tains, that the explosions and flames occur. The smut dust was prob- 

 ably ignited by static electricity in the cylinder of the threshing machine. 

 The drier the conditions, the more static electricity is formed, and the 

 easier it is to ignite the smut. 



The family Ustilaginace^ includes eleven American genera. Only 

 three genera out of the seven will be considered in this book. They are 

 UsHlago, Sorosporium and Tolyposporium. The genus Ustilago, of 

 which there are about seventy-two American species, is distinguished 

 from the other two less important genera by its single spores which 

 form dusty masses at maturity without any kind of inclosing membrane. 

 Sorosporium has its spores agglutinated into balls which form more or 

 less dusty masses. The spore balls are usually evanescent and the 

 spores are very dark. The spores are agglutinated into balls in Toly- 

 posporium, forming more or less dusty spore masses. The spore balls 

 are rather permanent, the spores adhering by folds, or thickenings of 

 the outer coat. 



Family 2. Tilletiace^.— The name Tilletia which is that of an 

 important genus (Fig. 63) of the family is derived from Matthieu Tillet, 

 who pubUshed a book in, Bordeaux, France, in 1755. The sori form 

 dusty spore masses, which break out to the surface, or are imbedded 

 permanently in the plant tissues, often without causing any malforma- 



' ASHLOCK, J. L.: Smut Explosions. The Country Gentleman, AprU 10, 1915, 

 p. 703. 



