68 PRACTICAL BOTANY. 



Bacilli, and Spirilla. The comma-shaped forms resemble 

 the Comma bacillus of cholera. Run iodine solution under 

 the cover glass and observe that the longer rods are made 

 up of segments. They are Leptothrix forms. Draw. 



2. Steep some vegetable matter of any kind in water. 

 Filter the solution into two flasks and boil for twenty 

 minutes. Stop both flasks with cotton- wool plugs. After 

 twenty-four hours repeat the boiling with the cotton-wool 

 plugs in the flasks. After another twenty-four hours 

 repeat the boiling. Now set the flasks away for several 

 days, allowing the cotton wool plug to remain undisturbed 

 in one; removing it from the other. 



Examine the flasks daily. Account for the fact that 

 the liquid in the closed flask remains unchanged, while 

 that in the open flask becomes turbid. Notice that a skin 

 forms on the surface of the liquid in the open flask, -- the 

 pellicle or zoogloea, stage of Bacteria. This pellicle begins 

 to form as soon as the conditions become unfavorable for 

 further growth by cell division. It is during this stage 

 that resting spores are principally formed. 



Examine under the microscope daily some of the liquid 

 from the open flask, using the high power. There will 

 usually be found at first a short rod form with rounded 

 ends and a constriction at the middle, Bacterium termo. 

 Later the longer rods and Leptothrix filaments of Bacillus 

 subtilis will be abundant. Other forms may be present. 



3. Let five ounces of Pasteur's fluid with much sugar 

 receive a little yeast and work for a day or two. Kill the 

 yeast by heating above 50 C. Set aside for two or three 

 days and then examine the liquid below the zoogloaa. 

 Spread a little on a cover glass in a thin, even layer, dilut- 

 ing with water if necessary, and let it dry in the air. 

 Then, holding the cover glass, prepared side up, with the 

 forceps, pass it several times back and forth through the 

 hot air just above a gas flame to fix the Bacteria thoroughly 



