214 TEXT-BOOK OF FUNGI 



sulphate of copper, or some other fungicide. Such treat- 

 ment sometimes proves beneficial, sometimes not. 



Brefeld has recently published an account of his investi- 

 gations on the infection of cereals and other plants by 

 'smut' (Ustilago) spores. As the result of numerous 

 experiments he has proved that in the case of wheat, 

 barley, and certain other plants of no economic import- 

 ance, infection takes place through the flower, and not 

 during the seedling stage in the ground. Spores carried 

 by wind, insects, or in the case of aquatic plants by water, 

 are deposited on the stigma, where they germinate and 

 pass down into the ovary or young seed. There a certain 

 amount of hybernating mycelium is formed which remains 

 in a resting condition until the seed is sown, when the 

 mycelium grows along with the plant, and finally produces 

 the well-known sooty mass of smut spores in the seed. 



In this instance it will be observed that infection takes 

 place in one generation, and the fungus produces fruit in 

 the next generation of the host-plant ; the interval having 

 been tided over by the presence of hybernating mycelium 

 in the 'seed.' Spores are, however, necessary to secure 

 infection in the first instance. 



Brefeld showed that oats and some other plants can 

 only be infected during the seedling stage, by spores 

 present in the soil. 



Farmers are well aware that, by proper treatment of the 

 ' seed,' smut can be reduced to a minimum in the case of 

 oats, whereas smut in barley cannot be prevented by the 

 same line of treatment. Brefeld's discovery has furnished 

 the explanation. Smut in oats is the outcome of infection 

 during the seedling stage, due to the presence of spores 

 adhering to the seed. Hence, if such seed is treated, the 



