FUNGI 211 



the bread, and the bread is then put into a warm place to 

 rise or, more exactly, to grow yeast plants. If the mate- 

 rials and the temperature are right, the yeast plants grow 

 very rapidly, feeding upon the material of the dough and 

 changing the sugar into carbon dioxide " and alcohol. 

 Little bubbles of gas are developed throughout the dough, 

 making it slightly porous. 



The bread is then kneaded to mix the greatly inerqapd 

 number of yeast plants still more thoroughly and is allowed 

 " to rise " again. The plants are by this time?fvery uni- 

 formly scattered through the dough and they develop little 

 bubbles of carbon dioxide throughout the mass so that a 

 light sponge results. When this is heated in the oven, 

 the tiny bubbles of gas expand, making a more porous 

 sponge, the alcohol evaporates, and the dough hardens, thus 

 forming light bread. Although the study of these minute 

 fungi is very interesting, it must be done by aid of the 

 microscope and will not be attempted here. 



We are most of us familiar with some of the larger 

 fungi such as the mushrooms (Fig. 103) and toadstools. 

 Mushrooms are widely used as a delicacy 

 and their growth is an important indus- 

 try in somejsections. They are grown in 

 soils very rich in humus and generally 

 in dark, cellar-like places. The mush- 

 rooms that grow wild in the woods are 

 abundant in some localities but should 

 not be used for food unless most care- Fi 103 



fully examined by some one who is 

 expert in determining the different species. There are 

 several species of mushrooms which are exceedingly poison- 

 ous. For one of these there is no known antidote. The 

 general structure of these larger fungi can be seen by 

 examining a mushroom obtained from the market. 



