SPAWN-MAKING 



pure culture is transferred to such a sterilized tube, using 

 for this transfer sterile needles, or scalpels, there will be 

 little danger from foreign organisms, and the piece of my- 

 celium inserted will therefore grow as a pure culture free 

 from all other fungi or bacteria." . . . 



"In making pure cultures of mushrooms, large test tubes or 

 wide-mouthed bottles may be used. These should be care- 

 fully cleaned, and if possible, a sterilization should be given 

 by means of dry heat as a preliminary precaution. In this 

 event the tubes are plugged with cotton plugs and placed in 

 a dry oven made for the purpose. They are heated to a 

 temperature of about 150° C, and this temperature should 

 be maintained for nearly an hour. Ordinarily, however, in 

 rough work it is not essential to employ this preliminary 

 sterilization. In either case the tubes are next partially filled 

 (about two-thirds) with the manure, or half-decayed leaves, 

 upon which it is desired to grow the virgin spawn. A plug 

 is inserted in each tube, and the tubes are then sterilized in 

 a steam boiler or under pressure. If sterilized under steam 

 pressure, as in an autoclave, it is necessary to use about 15 

 pounds pressure and to allow the tubes to remain at this 

 pressure for from 15 minutes to half an hour. If the steriliza- 

 tion must be effected in a boiler or in an open water bath, 

 it can only be done at 100° C, of course; and it is then 

 desirable to boil the tubes for at least an hour on each of 

 two or three successive days. 



"With the tubes thoroughly sterile, the next step is to make 

 the cultures or inoculations. By the tissue-culture method it 

 is implied that the inoculations are made from pieces of the 

 tissue of a living mushroom. It is at this stage that selec- 

 tion may be made. One should procure from a bed of mush- 

 rooms in full bearing mushrooms which represent the most 

 desirable qualities that are to be found. Size, quality, and 

 general prolificness must all be considered, as well also, as 

 other characteristics in any special selections. One may de- 

 sire, for instance, to select from a variety which yields through- 

 out a long period or one which is resistant to higher tem- 



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