CULTIVATION OF MUSHROOMS. 257 



the inoculation is very certain and very abundant, so that a large 

 number of spores would be present in the manure from horses fed in 

 this way. 



The natural spawn also may originate from spores which are 

 carried by the wind from the pasture or meadow mushrooms upon 

 manure piles, or especially from spores which may lodge in the dust 

 of the highways or street. Many of these spores would cling to the 

 hoofs of the horses and at night, or at times of feeding, would 

 be left with the manure in the stall. At other times horse drop- 

 pings may be gathered from roads or streets where spores may be 

 present in the dust. The piles of the droppings accumulated in this 

 way, if left a sufficient time, may provide natural spawn by this 

 accidental inoculation from the spores. 



Probably few attempts have been made to grow the natural 

 spawn with certainty in this country, though it does not appear to 

 be an impracticable thing to do, since formerly this was one source 

 of the virgin spawn in Europe. It is usually obtained by search 

 through stables and barn yards or other places where piles of horse 

 manure have accumulated and have remained for several months. 

 In some cases the growers keep men employed through the summer 

 season searching the yards and stables over a considerable area for 

 the purpose of finding and gathering this natural spawn. It is prob- 

 ably termed virgin spawn because of its origin under these natural 

 conditions, and never having been propagated artificially. 



The natural spawn, as indicated above, is employed for a variety 

 of purposes. It is used for inoculating the bricks in the manufac- 

 ture of brick spawn. It is used for propagating once or twice in the 

 mushroom beds, for the purpose of multiplying it, either in the man- 

 ufacture of brick spawn, or for flake spawn, which is planted 

 directly in the beds to be used for the crop. In some places in 

 America it is collected on a large scale and relied on as the chief 

 source of spawn for planting beds. In such cases the natural or 

 virgin spawn is used directly and is of the first and most vigorous 

 generation. It is believed by growers who employ it in this way 

 that the results in the quality and quantity of the crop exceed those 

 produced from the market spawn. But even these growers would 

 not always depend on the natural spawn, for the reason, that col- 

 lecting it under these conditions, the quantity is certain to vary 

 from year to year. This is due probably to varying conditions of 

 the season and also to the varying conditions which bring about the 

 chance inoculation, or the accumulation of the material in the yard 

 for a sufficient amount of time to provide the mycelium. 



