PLANTS WHICH CAUSE DECAY 401 



count of their hulls, from eighteen to forty hours), and 

 then dried (this is hastened by dusting them with 

 plaster or slaked lime) before sowing. Very favorable 

 results have been obtained with oats by dipping for 

 ten minutes in formalin (one pint of formalin in thirty- 

 six gallons of water) . Other precautions, in addition 

 to the use of germicides, are to grow some other crop 

 besides Grain until the spores in the soil are dead (two 

 or three years) ; to keep cattle and manure off the 

 land where there is any danger of carrying the spores, 

 and to disinfect the barn, bin, thresher, etc. The loss 

 in the United States from Oat -smut alone is estimated 

 at over $18,000,000. 



If these Smuts occur in your vicinity, it will be 

 very easy to watch the germination of the spores in 

 hanging drop cultures, and also to make experiments 

 to determine the relative value of germicides and 

 whether they impair the germination of the seed. If 

 clean seed is obtainable, infections may be made. 



The Black Stem Rust of Grain has a very different 

 appearance and mode of life from the Smuts of Grain. 

 Instead of being confined to the flowers, it appears on 

 the whole plant, principally on the stalks and leaves, 

 where it forms. elongated black ("black rust") or red 

 ("red rust") pustules. The red pustules contain one- 

 celled spores (called summer spores or uredorspores) , 

 as is shown in Fig. 224; the black pustules contain 

 two -celled spores (called autumn spores or teleuto- 



