MUSHROOM GROWING 



called that a special technique is required, 

 since otherwise the presence of foreign 

 moulds or bacteria will cause the pieces of 

 tissue to undergo prompt decay, rather than 

 to grow into a vigorous mycelium. The use 

 of these pure culture methods indeed neces- 

 sitates a knowledge of sterilization precau- 

 tions, and of the distribution of bacteria and 

 moulds in nature. 



Making pure cultures. The method of 

 making pure cultures is described in bulle- 

 tin 85, Bureau of Plant Industry, United 

 States Department of Agriculture as fol- 

 lows : 



"The materials, or media, and all the vessels employed 

 must be sterilized, which implies being heated at a tempera- 

 ture sufficient to kill all germs present in the vessels or 

 materials used. If the vessels used are test tubes or other 

 pieces of glassware with small mouths, they should, previous 

 to sterilization, be plugged with cotton batting. This cotton 

 batting prevents, when carefully manipulated, the entrance of 

 germs from the air, and therefore keeps the vessel or medium 

 in a pure or sterile condition. If such a vessel is opened, 

 this should be done in a room free from currents of air or 

 falling dust particles; and, while open, tubes and other ap- 

 paratus should be held in a more or less horizontal position, 

 so that they will be less liable to contamination. It follows, 

 of course, that the cotton plug, if removed, should not come 

 in contact with any unsterilized substances. If, now, a small 

 quantity of the growing mycelium of a mushroom from a 



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