Igo NATURE STUDY AND AGRICULTURE 
sound apple aside for about a week and watch for the result. How do 
you explain it? (Apple rots are caused either by fungi or by bacteria.) 
4. Different methods of infection. — Find out in what different ways 
plants may become infected with disease-producing fungi. 
5. Multiplication of bacteria. —It has been computed that if a 
bacterium divides once every hour, its offspring at the end of two days 
would number 281,500,000,000. What would be the number at the end 
of the first 24 hours? Notice that there will be twenty-four multiplica- 
tions, giving us these products: 2, 4, 8, 16, 32, 64, etc. to the 24th. 
6. Plant diseases in your district. — Find out what plant diseases 
are prevalent in your region. Which are the worst? How may each 
be controlled ? 
7. Identifying diseases. — (a) Try to find actual cases of all the 
plant diseases that are prevalent in your region, and to make yourself 
familiar with their appearance. (6) If you find some plants that look 
unhealthy, try to identify the diseases they are troubled with. 
8. A collection. — Make a collection of leaves and stems showing 
rust, smut, mildew, bean-pod spot, or other diseases. Label the 
specimens and preserve them for future use. 
9. Fungicides. — A fungicide is a substance used to kill, or to prevent 
the growth of fungi. Watch for an opportunity to see some farmer or 
gardener treat his seeds or plants with afungicide. Give a clear descrip- 
tion to your class — material used, seed or plants treated, method of 
application, etc. 
10. Grain rust. — (a) If rust is found in any of the grain fields of 
your vicinity, examine the appearance of the plants and note how and 
where the disease manifests itself. Let a good farmer show you if 
necessary. The reddish or blackish spots on the surface of the leaves 
and stems are clumps of spore cases, the main part of the fungus being 
within. (6) Do you notice any difference in color between the rust 
spots in the later stage of the plant’s growth as compared with the spots 
in early summer? (c) If there are any barberry bushes in your vicinity, 
go and see them and try to find rust spots upon them, in June or July. 
11.- Smut. — When grain is headed out in your district, try to find 
some smutted heads. Examine them and notice that the black mass 
consists of innumerable tiny specks. These are the spores of the smut 
fungus whose fibers extend through the body of the entire host plant. 
Mention all the grains in which you have found smut, — as wheat, oats, 
