MUSHROOM GROWING IH THE UNITED STATES 7 



grade of pure-culture spawn originating from germinated spores 

 and, because of large-scale production and competition, are able to 

 sell spawn cheaper than the average grower could produce it at 

 home. 



A list of established spawn makers will be furnished on request 

 by the Division of Mycology and Disease Survey, Bureau of Plant 

 Industry, United States Department of Agriculture, Washington, 

 D. C. 



VARIETIES 



Several distinct varieties of the common mushroom are cultivated, 

 but for convenience the trade has grouped them according to the 

 color of the cap, as white, brown, and cream. The terms white 



Figure 6. — Apparatus used to prepare compost for filling spawn bottles 



and brown refer to distinct varieties, but there are several cream 

 varieties. The white variety usually commands the highest price 

 on the market, owing to its color. It is prolific but is far from 

 ideal because of its tendency to stain when bruised by handling 

 and to produce clusters on the beds and an excess of button mush- 

 rooms. The brown variety is discriminated against in most mar- 

 kets but has advantages over the white in better shipping quality, 

 firmer flesh, and production of fewer button mushrooms. Cream 

 mushrooms are intermediate in color and combine the other charac- 

 teristics of the white and the brown in different degrees, depending 

 on the variety. 



It has been customary to consider all cultivated mushrooms as 

 varieties of Agaricus campestris. However, there are undoubtedly 



