COPPER SULPHATE (BLUE VITRIOL). 219 



twelve hours' steeping remove the seed and spread it on a board. It 

 must be turned frequently. By this prolonged immersion and stirring 

 the air adhering to the grain, often with tenacity, is gradually dis- 

 placed, and the liquid touches their whole surface. Corn-seed so 

 treated does not keep. Like all grain moist:'ned and swollen by 

 steeping it heats and spoils ; blue vitriol then exerts a deadly action on 

 the seed and kills a large quantity. It is thus absolutely necessary to 

 sow the corn-seed as soon as possible, and as soon as it is dry again. 

 If the operation be commenced at, 4 o'clock in the morning it is 

 finished in the evening ; the next morning the corn-seed disinfected 

 by the blue vitriol is bagged up in sacks, conveyed to the field, 

 and sown as soon as possible. In spite of all precautions, loss in 

 using this process is unavoidable, for the blue vitriol is concentrated, 

 in drying, around the grains, where it acts as a concentrated solution. 

 To remedy this drawback weaker solutions have been tried. If grains 

 are only immersed for fifteen minutes in a O'O per cent solution they 

 undergo no damage, and 99 per cent germinate, often even before the 

 untreated grain ; after steeping for three hours the grain does not 

 germinate until three days after the untreated grain (experiment on 

 oats, variety Scotch "White Superior). 



Bloymeyer advises a still shorter immersion, carried out thus : 

 Eun the corn-seed into a basket and dip that for one minute into a 

 1 per cent solution of blue vitriol. Drain and dfy. If the time of 

 steeping be considerably shortened, it is owing to the great concentra- 

 tion of the bath of blue vitriol. Herzberg found that the temperature 

 of the blue vitriol solutions played a very important role. Below 

 8° C. the blue vitriol bath is, so to speak, without action on the spores 

 of Ustilago (smut), whilst a solution at 24°-26^ C, even if it only contain 

 0-1 per cent of blue vitriol, kills them instantly. This is explained by 

 the fact- that the spores are very resistant, but that the sporidia are 

 very sensitive. By inducing their formation by a high temperature, 

 the above resul- is obtained ! Herzberg, therefore, recommends 

 steeping for twenty-five hours in a 0*1 per cent solution at 25° C. 

 The spores of Tilletia (bunt) do not behave similarly. They rather ap- 

 pear to be more sensitive to cold solutions ; the most favourable tem- 

 perature is from 6°-8° C. At that temperature a solution of 0-0004 

 per cent prevents their future evolution. This fact was pointed out by 

 Prevost as far back as 1807, who gave 6^" and 7^" C. as the extreme 

 temperatures to which these spores are most sensitive ; at the ordinary 

 temperature the immersion ought to last half an hour in a 0"05 per cent 

 solution ; at a higher temperature these solutions, therefore, have no 

 action. Wheat, therefore, infected with germs of Tilletia (bunt) ought 

 to be disinfected, according to Prevost and Herzberg, at a low tempera- 

 ture, whilst barley and oat seed infected with Ustilago (smut) should be 

 disinfected between 24° and 26° C. Treatment by blue vitriol alone 

 is abandoned now, because it is too often deadly. An injurious 

 action has been found on grain after steeping one hour in a 0"1 per 

 cent solution. The growth of the radicles is often affected to such 

 a point that they do not form although the plumule may be long 

 enough. When the radicle emerges its point is brown, and remains. 



