Diseases of Plants 309 



determined with reasonable certainty from personal 

 knowledge, from such literature as may be at hand, 

 or from persons who may readily be consulted, then 

 the county agricultural agent or the state agricultural 

 experiment station should be written to. When writing 

 for inlormation, it is well to send specimens from dis- 

 eased plants (or if the trouble is caused by insects, a 

 few of these), with a full description of the conditions. 

 Although children cannot be expected to handle poisons 

 used in seed treatment or in sprays, they can observe how 

 these remedies are applied and they can readily learn to 

 recognize the symptoms of many diseases and insect 

 pests. If there is a microscope in the school, demon- 

 stration of the spores of many parasitic fungi may readily 

 be made. Such a demonstration may often be arranged 

 through school authorities or through the county agri- 

 cultural agent. An acquaintance with the world of 

 microorganisms all about us may well be begun in this 

 manner. 



Questions 



Why are the garden plants considered as belonging to the 

 higher forms of plant life? Name some seedless plants. Name 

 some common plants that do not have green coloring matter. 

 How do fungi reproduce ? 



What are parasites ? Why did the causes of many plant diseases 

 long remain a mystery? How may the gardener recognize the 

 presence of disease in his plants ? 



How does the clubroot disease of cabbage affect the plant it 

 attacks? How is it controlled? How can the clubroot disease 

 be distinguished from the root-knot disease of cabbage? What 

 causes bacterial wilt of vine crops? Describe the activities of 

 the parasite. How does it gain an entrance to the host plant ? 

 What are the best means of controlling the disease? Describe 



