256 Introduction to Botany. 



high power. A various assemblage of small objects will be 

 seen. Run a drop of iodine under the coverglass ; the ob- 

 jects colored blue or almost black by this reagent are starch 

 grains, which make up the bulk of a cake of yeast, while 

 the round or oval yellowish bodies are yeast plants. The 

 still smaller rods and rounded bodies are bacteria. Some of 

 the yeast plants will be found in the process of reproduc- 

 tion by budding (Fig. 133, a). Yeast plants are efficient 

 in making bread light, as will be shown in the discussion. 



150. Mix about two teaspoonfuls of molasses with a 

 pint of water and add a small piece of yeast cake. Fill a 

 wide-mouth bottle with the mixture and invert it in a dish 

 of the same. To keep the liquid from running out of the 

 bottle while inverting it, fill the bottle quite full and place 

 a piece of stiff paper over the mouth and hold the paper 

 in position with the tips of the fingers while inverting the 

 bottle and placing it in the dish ; then remove the paper. 

 Keep the preparation in a warm place. After a time 

 bubbles of gas will arise and displace the liquid. When 

 a sufficient quantity of gas has been secured, it can be 

 demonstrated to be carbon dioxide by the methods de- 

 tailed on page 13. The solution will now be found to 

 have an alcoholic taste, and, if it is properly distilled, 

 alcohol can be obtained strong enough to burn. 



DISCUSSION. 



152. Nature of Bacteria. — The bacteria are the smallest 

 of known plants, the rounded forms being about .0001 mm. 

 in diameter; the oblong and rod-shaped forms are no greater 

 than this in their short diameter, as a rule, and their long 

 diameter is from i|- to 5 times as great. They are there- 

 fore still very small in appearance, even when magnified 

 with the highest powers of the microscope, and it is difficult 



