298 THE ESSENTIALS OF AGRICULTURE 



QUESTIONS AND PROBLEMS 



1. What are the most important plant diseases of your locality? of 

 your state ? 



2. Secure from your county assessor a statement of last year's produc- 

 tion of wheat, oats, or barley. Assuming that 5 per cent of the crop was 

 destroyed by smuts and 5 per cent by rusts, estimate what these diseases 

 cost your county last year ? 



3. How do plant parasites and plant saprophytes differ? 



4. Describe the parasitic flowering plant known as dodder. 



5. What are bacteria and fungi? Are all bacteria and fungi parasitic? 



6. What are the more important methods of distribution of bacteria 

 and fungi ? 



7. What are the principal methods of control of plant diseases ? 



8. What methods of controlling or preventing plant diseases are used 

 in your locality ? 



9. Secure an agricultural experiment station bulletin giving directions 

 for treating wheat and oat seed for smut, and prepare a brief specific outline 

 of the things that should be done. 



10. Describe some methods of sanitation to prevent plant diseases. 



11. What is meant by quarantine against plant diseases? Does your 

 state enforce such quarantine? 



EXERCISES 



1. A study of bacteria. 



MATERIAL : A compound microscope with equipment ; a piece of stale 

 bread ; and a tumbler of water. 



Place a small piece of bread in a tumbler of water and let it stand 

 twenty-four to forty-eight hours. Examine a drop of the liquid under 

 the microscope. A large number of forms of bacteria will be noticed ; 

 also small animals are likely to be present. Some of the bacteria will 

 appear to be spherical, others rodlike, often forming long chains. 

 Many swim rapidly across the field. 



2. Bacteria from soil and air. Boil some sweetened water in three 

 glass flasks until all life in the water is destroyed (ten minutes). 

 After the water has cooled, drop a piece of field soil into one flask. 

 Allow another flask to stand exposed to room atmosphere for twenty- 

 four hours. Keep the other flask constantly closed. After three days 

 make a microscopic study of some of the water from each flask. 



