Chapter 8. 
FUNGI AS A CAUSE OF DISEASE IN PLANTS. 
Common fungi, mushrooms, toadstools and moulds. How they 
live. Saprophytes and Parasites. The ‘‘Damping off’ disease 
of Seedlings caused by the fungus Pythium. Life Story, means 
of spreading and living in the soil, precautionary measures. 
In preceding chapters you have become acquainted with 
the normal uses of the parts of healthy green plants. We 
are now to consider plants in disease and especially the 
disturbances of the structure and functions of plants pro- 
duced by parasitic fungi. It is obviously impossible 
within the limits of a few chapters to deal with the whole 
subject of diseases of plants caused by fungi, but by a 
consideration of some of the diseases most common in 
fields, gardens and greenhouses, the main features of the 
subject may be illustrated. By this treatment you will 
not only become more familiar with the causes of these 
particular diseases, but also with the sort of* precautions 
and remedial measures it is worth while to adopt in rela- 
tion to the various types of plant disease. 
Practically all parts of plants are subject to disease. 
In some cases we have immediate and complete destruc- 
tion of the plant or part attacked, but in others the death 
may be delayed or the plant may support the parasite in- 
definitely. We have diseases of seedlings, diseases of 
roots, of stems and of leaves, and a very large class of 
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