1 906.] 



Mushroom Spawn Making. 



593 



purposes it is necessary to renew the spawn by obtaining material 

 known as virgin spawn which has not previously weakened 

 itself by the production of mushrooms. Natural virgin spawn 

 may be found wherever it has been possible for the spores to 

 germinate and produce a mycelium naturally. Ordinarily, such 

 spawn appears in compost heaps, rich garden beds, pastures, &c. 

 Many attempts have been made by practical growers to develop 

 spawn from spores, sowing the gill portions of mature mush- 

 rooms in specially constructed beds, but the results, so far as is 

 known, have not been satisfactory. As a rule, therefore, growers 

 rely upon virgin spawn obtained, as it were, by chance. Where 

 a spontaneous growth of spawn is observed trenches are dug, 

 and these filled with good stable manure, which in time becomes 

 penetrated, or the virgin spawn may be used in spawning the 

 brick or cake in which it is sold. 



This method, it will be seen, prevents much progress being 

 made in the selection of desirable varieties of mushrooms or in 

 the improvement of varieties ; but recently, as the result of 

 investigations carried out by Professor B. M. Duggar on behalf 

 of the United States Department of Agriculture,* a method of 

 making " tissue cultures " has been discovered, which admits of 

 cultures being made of any desirable species or varieties. The 

 use of this new method has, it is stated, been the means of 

 advancing the industry of spawn making in the United States 

 during the past two years. It is pointed out, however, that the 

 pure culture method of making virgin spawn is not one which 

 will prove successful in the hands of wholly inexperienced 

 persons or of those unwilling to spend time and use the utmost 

 care in the manipulation of the cultures and the culture material. 

 The method described by Professor Duggar is summarised below. 



In making pure cultures of mushrooms large test tubes or 

 wide-mouthed bottles may be used ; these should be carefully 

 cleaned and, if possible, should be sterilised by dry heat as 

 a preliminary precaution. For this purpose the tubes should be 

 plugged with cotton, placed in a dry oven, and heated to a tem- 

 perature of about 150 deg. C. for nearly an hour. Ordinarily, 

 however, in rough work it is not essential to employ this 

 preliminary sterilisation. In either case the tubes are next 



* " Bureau of Plant Industry," Bull, No. 85. 



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