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THE BOOK OF WHEAT 



presence of the smut can scarcely be detected without the aid 

 of a microscope. A mass of smut threads then absorbs all 

 the nourishment, fills the flower or grain, and soon converts 

 it into a mass of spores. As the parasite lives at the expense 

 of its host, the latter is weakened and stunted in proportion to 

 the amount of smut. This may be great enough to dwarf the 

 plants so as to prevent the formation of heads, or even to 

 cause the stalks to die back to the ground, or it may be so 

 little that the heads are never reached, simply the straw being 

 infected. Much of the straw may be thus infected, greatly 

 reducing the yield, even though apparently uninjured heads are 

 formed. Smut filaments have also been found in grains which 

 had formed starch. 1 In general, smut and wheat seem to de- 



SECTIONS OF SMUTTED WHEAT STRAW 



At the left is a longitudinal section of a wheat straw and at the right a cross 

 section, a, epidermal cells ; b, smut filaments ; c, fibrous cells ; d, internal 

 tissues. 



mand about the same meteorological conditions for their best 

 growth. Smut will successfully pass the winter, even upon 

 the open ground in North Dakota. Germs two years old have 

 not lost their power of producing smut in a crop. 3 



Grains of wheat affected by stinking smut are slightly larger 

 and more irregular than healthy ones. Such kernels, the so- 

 called "smut-balls," are easily broken open, and the dark- 

 brown powder with which they are filled has a very disagree- 

 able and penetrating odor that pervades the whole bin of 

 wheat, even if only a small per cent of the kernels are smut- 

 ted. On this account they differ from all other grain smuts 

 in that their presence can be easily recognized. Sometimes 



1 Bolley, Proc. Tri-State Grain Growers' Ass'n., 1900. p. 86. 

 8 Rept N. D. Agr. Exp Sta., 1901, p. 34. 



