330 



ECOLOGY. 



mushroom lives in the ground, and grows here for several months 

 or even years, and at the proper seasons develops the mature 

 mushroom plant. The mycelium lives on decaying organic mat- 

 ter, and a large number of the threads grow closely together form- 

 ing strands, or cords, of mycelium, which are quite prominent 

 if they are uncovered by removing the soil, as shown in fig. 434. 

 616. From these strands the buttons arise by numerous threads 

 growing side by side in a vertical direction, each thread growing 

 independently at the end, but all lying very closely side by 



Fig. 435- 



Agaricus campestris; sections of "buttons" of different sizes, showing formation of gills 

 and veil covering them. 



side. When the buttons are quite small the gills begin to form 

 on the under margin of the knob. They are formed by certain 

 of the threads growing downward in radiating ridges, just as many 

 of these ridges being started as there are to be gills formed. At 

 the same time, threads of the stem grow upward to meet those at 

 the margin of the button in such a manner that they cover up 

 the forming gills, and thus enclose the gills in a minute cavity. 

 Sections of buttons at different ages will show this, as is seen 

 in fig. 435. This curtain of mycelium which is thus stretched 

 across the gill cavity is the veil. As the cap expands more 

 and more this is stretched into a thin and delicate texture as 



