LOW FORMS OF PLANT LIFE 371 



The mold spores on the bread will germinate and send 

 their root-like threads into the bread to absorb the food. 

 In a day or two these threads in the bread will be large 

 enough to send up above the surface some threads with 

 black knobs on the end. Each knob is full of ripe spores 

 waiting to be carried away by the air. 



Yeasts are fungi, and there are many kinds of them. 

 They are harmful when they grow 

 on fruits and in fruit juices which 

 we want to keep for some time. 

 They are useful for producing car- 

 bon dioxide to raise bread, and YEAST CELLS WITH BUDS 

 for fermenting grains and other 

 substances for the production of commercial alcohol. 



To see yeast plants with the microscope: Mix a small 

 piece of soft commercial yeast in a little water containing 

 a small amount of sugar, let it stand an hour or so, and 

 then take a drop of the liquid and place it on the micro- 

 scope slide. The oval-shaped bodies are yeast. 



255. Bacteria compose a group of fungi of about 

 1,000 kinds, of which about 20 are parasitic to man and 

 cause disease; the others are useful or harmless. These 

 parasitic bacteria can live on man because of improper 

 methods of living on the part of most people. Man's 

 uncleanness and over-indulgence are largely responsible for 

 the existence of parasitic bacteria which produce disease. 



Bacteria are useful in causing the decay of useless dead 

 matter, which can then be used by growing plants. They 

 are absolutely essential in the soil to produce foods for 

 various plants. Most plants have to have their particular 

 kind of bacteria in the soil or they cannot grow. Bacteria 

 are also useful in preparing certain foods. Cheese and 

 butter are examples. 



