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 immxediate 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 



57 



