118 REPRESENTATIVE PLANTS 



bottle and stopper with a cork ; do the same for No. 4, but 

 use cotton for a stopper. Place all in some moderately 

 warm place and watch carefully for any change in appear- 

 ance and odor. After about three or four days, what do 

 you find, and how do you explain ? 



2. Boil some pieces of potato until cooked but still firm. 

 Plunge a tumbler and saucer into the boiling water, and 

 with a boiled needle, pick out a piece of potato, place on boiled 

 saucer, under boiled tumbler; surround the base of the 

 tumbler with cotton. Allow the second piece of potato to 

 cool and place on the other saucer without any precautions. 

 Set both away in a warm i)lace for four or five days, and 

 then examine for appearance and odor. What do you find ? 

 Explain as before. 



The experiments may be varied by placing the tumbler 

 in a cool place. 



3. Take two small cubes of fresh meat ; dry one quickly 

 and thoroughly over a fire, taking care not to cook it. 

 Place both pieces under tumblers for three days and then 

 examine. Observe the results, and explain them. 



Matters to investigate. Read about the various methods 

 of preserving foods from spoiling ; i.e. plans to prevent the 

 growth of bacteria, molds, and ferments (yeasts). 



Discuss, in your paper on bacteria, the economic impor- 

 tance, if possible, of bacteria, and the good as well as the 

 injurious effects that come from their growth. 



A few questions may assist in the direction of effort to 

 understand these minute forms of life : — 



1. What importance are bacteria to the farmer in soil 

 renovation ? 



2. What plant family is intimately associated with bac- 

 teria, receiving much benefit therefrom ? 



3. What are antitoxins ? 



4. What life habits have bacteria? How do they mul- 

 tiply, and how rapidly ? 



