CHAPTER XXI 



FUNGUS DISEASES OF PLANTS 



216. Many plants of the farm and garden are subject 

 to attack by various kinds of minute plants, known as 

 fungi. The "rusts" of small grains, plum trees and cot- 

 ton, are familiar examples. Also, the " mildew" of grapes 

 and roses. These fungi are thread-like plants. Some 

 form their thread-like bodies inside of the plant tissues, 

 such as the "smuts" and "rusts." (Fig. 87.) Other 

 forms, like the mildew, grow on the surface of the 



leaves and stems, but 

 send little root -like 

 branches (Fig. 89) into 

 the plant tissue to 

 absorb its substance. 

 Another class of fungi, 

 known as bacteria, 

 never form "threads," 

 or hyphce, as they are 

 called by the botanist, 

 but only cells. Some 

 species of bacteria cause 

 disease. The cells are 

 formed inside of the 

 plant body. 



216. How Fungus 

 Plants Get Their Food. 

 Fungi do not have the 

 green chlorophyl (^ 48), 



Fig. 87. A, head of oats affected with smut, 

 the chaff being only partially destroyed; 



B, head of oats decidedly smutty, but 

 having the chaff only partially destroyed; 



C, final stage of oat smut, showing con- 

 dition at harvest time 



(146) 



