606 IOWA ACADEMY OF SCIENCE 



Kellerraan and Swingle (33) in their report of 1890 show- 

 that vapors of chloroform, carbon bisulphide, ether, ammonium 

 hydrate, and sulphurous oxide were all ineffective. At that time 

 formalin vapor was not used in their experiments. 



Prior to 1899 Bolley had secured satisfctory results with the 

 formalin solution (1 to 50). However, he recognized the ob- 

 jections that would be raised against any treatment which neces- 

 sitated wetting the grain. In 1897 and 1898, Bolley ascertained 

 that the gas treatment was effective, but was not positive of its 

 use on a large scale. Following later experiments the author 

 (6-87) concludes that for the gas to be effective it is necessary 

 to have it accompanied by a vapor dense enough to form a film 

 over the surface of every grain. The dry gas has no effect on 

 the smut spores. The vapor factor again brings in the objec- 

 tion raised against solutions; however, the gas treatment is to 

 be preferred for extensive work. 



Clinton (1898) found that carbon bisulphide fumes were not 

 effective, but work with stronger solutions of formalin applied 

 in smaller amounts was very promising. In cases of too strong 

 a solution the vitality of the grain was injured. 



Wheeler (60) of the South Dakota Station (1904) conducted 

 some preliminary experiments with various vapor treatments 

 for stinking smut of wheat. These experiments included for- 

 maldehyde, ammonia and chloroform. The apparatus used for 

 the gas treatment is described as follows : 



It consists of a hand blower (a), a cylinder containing the 

 grain (c), a test tube to contain the fungicide (b) and tubes 

 for connection. The air is forced by means of the blower 

 through the liquid fungicide in the test tube. From there it is 

 conducted by a tube to the lower part of the cylinder contain- 

 ing the grain and up through the seed grain. The air permeated 

 with the fungicide vapor is taken up from the cylinder by the 

 blower and forced through the liquid fungicide. By repeated- 

 ly passing the same air through the fungicide, it was thought 

 that a saturated atmosphere would be secured and greater uni- 

 formity of results obtained than if the air were passed only 

 once through the fungicide. 



The following treatments were considered in this preliminary 

 work: The grain was exposed to the formaldehyde vapor (40 

 per cent solution) for the following periods of time %, %, 

 \y-2, 2, 2y 2 , 3 hours, both with and without return current. 

 (See tables XV and XVI.) 



