MUSHROOM GROWING IN THE UNITED STATES 5 



ditions in filtered air before the veil is broken, and the mushroom 

 will continue to expand and produce spores even after it has been 

 surface sterilized, peeled, or cut up. Different procedures may 

 be followed to prevent spores of molds on the surface of the mush- 

 room from contaminating the cultures. Stems may be removed and 

 the surface layer peeled off with sterile forceps ; the mushroom may 

 be surface sterilized by flaming it or soaking it in a disinfectant ; or 



Figure 4. — Mushroom bottle spawn 



the spores may be transferred directly from the gills, or from spore 

 " prints " made by suspending the treated mushroom over a sterile 

 surface in a sterile container. 



The spores are transferred for germination either directly to sterile 

 washed compost or first to agar media to make certain that the 

 culture is free from contaminating molds and bacteria. Ordinary 

 potato-dextrose agar and beer-wort agar are suitable media. If the 



