6 STUDIES OF AMERICAN FUNGI. 



on vegetables. One of the molds, so common on bread, forms at 

 first a white cottony mass of loosely interwoven threads. Later the 

 mold becomes black in color because of numerous small fruit cases 

 containing dark spores. This last stage is the fruiting stage of the 

 mold. The earlier stage is the growing, or vegetative, stage. The 

 white mycelium threads grow in the bread and absorb food substances 

 for the mold. 



Mushroom Spawn is in the Form of Strands of Mycelium Now in the 

 mushrooms the threads of mycelium are usually interlaced into 

 definite strands or cords, especially when the mycelium is well 

 developed. In some species these strands become very long, and 



FIGURE 5. Agaricus campestris. Nearly mature plants, showing veil 

 stretched across gill cavity. (Natural size.) 



are dark brown in color. Each thread of mycelium grows, or in- 

 creases in length, at the end. Each one of the threads grows inde- 

 pendently, though all are intertwined in the strand. In this way 

 the strand of mycelium increases in length. It even branches as it 

 extends itself through the soil. 



The Button Stage of the Mushroom. The "spawn' stage, or 

 strands of mycelium, is the vegetative or growing stage of the mush- 

 room. These strands grow through the substance on which the 

 fungus feeds. When the fruiting stage, or the mushroom, begins 

 there appear small knobs or enlargements on these strands, and 

 these are the beginnings of the button stage, as it is properly called. 

 These knobs or young buttons are well shown in Fig. 3. They 



