Suggestions for Laboratory Work to Precede Chapter Nineteen 



1. Bacteria and molds may be grown for study by placing bread 

 and slices of boiled potato in moist chambers (tumblers inverted 

 in saucers). 



2. Place cultures under different temperature conditions and 

 note the effect of temperature on the rate of growth. Dry a part 

 of the bread and potato slices somewhat, and compare the growth 

 of bacteria and fungi on the dry slices with the growth of those on 

 the moist and wet slices. What do these experiments suggest re- 

 garding methods of avoiding bacteria and molds ? 



3.' In test tubes, yeast may be grown in sugar solutions from 

 commercial yeast cakes. The formation of carbon dioxid and 

 alcohol should be noted. The cells, buds, and filaments may be 

 seen with a microscope. 



4. From grainfields in the summer, specimens of rusts and 

 smuts can be obtained, and they may be preserved by drying. 

 The cluster-cup stage of rusts is common on elder, crowfoot, bar- 

 berry, and Indian turnip. In the laboratory the spores may be 

 examined and injuries to the leaves noted. 



6. Mushrooms and toadstools may be collected in the woods at 

 all seasons. Study the relation of the fruiting body to the vegeta- 

 tive part of the plant. Dried material and specimens preserved 

 in strong alcohol will serve to show the variety of these plants. 



248 



