174 



THE PRINCIPLES OF AGRICULTURE 



fungi (rarely written funguses). As an adjective, the word is 

 written fungous, as a fungous disease. A fungoid disease is a 

 fungus-like disease, the exact origin of which may not be known 

 or specified. Rusts, mildews and leaf-blights are types of fun- 

 gous diseases. 



292fe. The plant or the animal upon or in which a parasitic 

 fungus lives is known as its host. The fungus injures its host by 



Fig. 69. Work of the four-lined leaf-bug a sucking insect on currant 

 foliage. 



robbing it of nutriment and sometimes by breaking up its cellular 

 structure, and by obstructing the breathing-pores and interfering 

 with the movement of its fluids. 



293Z>. Physiological troubles may be termed internal troubles, 

 although the germs which cause some of them enter from tha 



