214 ANNUAL REPORT. 



produced in this way. The plants known as fungi, however, have no 

 leaf-green and therefore are not able to provide themselves with food 

 from soil and air. They must derive their nourishment from either 

 living or dead organic matter. 



Different kinds of plants grow on different soils. Fungi choose 

 places of growth in much the same way that other plants do, but much 

 more closely. Some grow on almost any decaying vegetable matter; 

 others only on dead wood of some particular tree. A very large num- 

 ber grow only on living plants and commonly each species only on 

 plants of some particular family or species. Wheat rust grows on 

 various grasses, the orange rust of berry plants, only on raspberries 

 and blackberries, while corn rust is not known to occur on any plant 

 but Indian corn. 



Where do fungi come from ? How do they get there? They never 

 originate spontaneously but always from reproductive bodies called 

 spores, answering the purpose of seeds. These are very minute and so 

 light that they are borne in the air like dust, and some kinds are car- 

 ried in water. Under favorable conditions if they are brought to the 

 right kind of plant, as corn smut spores to corn, they germinate and 

 send out a slender tube which answers the purpose of a root, and makes 

 its way into the plant, often through breathing pores. Once inside, it 

 grows and branches, sending its threads in various directions among 

 the plant cells. Frequently special branches are produced, which 

 enter into the cell cavities and act as suckers to take up nourishment. 



Many fungi have different stages of development, reminding one 

 rather of insects in their transformations than of plants. Each stage 

 has its own kind of spores. Frequently different stages occur on dif- 

 ferent host plants, as in wheat rust. This produces on the wheat itself 

 yellow summer spores and blackish spores which live over winter. The 

 summer spores retain their vitality only a short time; only the blackish 

 spores can carry the fungus through the winter. In spring they may 

 germinate on a different plant, the barberry, and produce a third stage 

 there; the spores from this stage, in their turn, produce yellow rust on 

 the wheat. 



It has been claimed that where fungi grow on plants, the plants 

 first become diseased and weakened and the fungus comes afterwards, 

 following and not causing the disease. This may be true in some cases, 

 but in all ordinary cases of this kind the fungus is the true cause of the 

 disease. Certain conditions of weather are favorable to its development, 

 just as certain conditions are favorable to the development of any oth- 



