tiply very rapidly, and the mushrooms are attacked by them in 

 such numbers that within a day or two every appearance of fogging 

 off is made manifest. These insects may be readily, destroyed by 

 fumigation with carbon bisulphide, but prevention is the wiser course. 



Larvae of Flies — With good manure and under suitable condi- 

 tions larvae of mushroom flies are not usually injurious. Never- 

 theless, the larvae of the little fly, Phora minuta, may be troublesome 

 in warm weather. Fumigation, as previously suggested, may be 

 of service in order that the life of a bed may be extended somewhat 

 later into the warm season. 



14. Mushroom Sp£iwn 



The mycelium of the cultivated mushroom has long been known 

 commercially as "spawn." From early times it has been recognized 

 that mushrooms may be grown from spawn, and it is quite certain 

 that in all attempts to propogate mushrooms spawn has been used 

 for the purpose. 



A "Chance" Methou — For practical purposes it is necessary to 

 renew the spawn and to secure, if possible, spawn which has not 

 previously weakened itself by the production of mushrooms — known 

 as virgin spawn. Natural virgin spawn may be found wherever "in 

 nature" it has been possible for the spores to germinate and to 

 produce a mycelium. ^ 



Many attempts have been made by practical growers to develop 

 spawn from spores, sowing the gill portions of mature mushrooms 

 in specially constructed beds; but the results, so far as the writer 

 is aware, have not been satisfactory. As a rule, therefore, growers 

 have been compelled to rely wholly upon a virgin spawn which has 

 been obtained by chance. It is said that in the vicinity of Paris 

 some persons make a business of searching for this virgin spawn, 

 which they sell to the growers at a high figure. 



However adept persons may become in the identification of var- 

 ious varieties of spawn by odor, etc., this must be considered essen- 

 tially a chance method. 



A "Selective" Method. — From what has been said it will be per- 

 ceived that very little advancement could be made in the selection 

 of desirable varieties of mushrooms, in varietal improvement and 

 the like, so long as the chance method of securing spawn should 

 prevail. 



The successful germination studies with chemical stimulation 

 mentioned in this paper were soon overshadowed by the discovery 



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