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 information, 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 
microérganisms 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 
