THE SMUT FUNGI 229 



the injury most plainly. Some parasitic fungi, however, 

 develop upon the leaves and stems of other plants. The 

 Onion Smut is one of the most important of these. It attacks 

 the leaves and bulbs of seedling onions, giving them a char- 

 acteristic blackish appearance, and often ruining the crop. 

 The spores develop secondary spores called sporidia in 

 much the same way that other Smut diseases develop. 



The Onion Smut is especially troublesome on land in 

 which successive crops of onions are grown. This is be- 

 lieved to be due to the presence of the spores in the soil. 

 Consequently, a wise crop rotation is the first preventive 

 measure. The spores are also easily carried from field to 

 field in the soil adhering to hoes or other tools. Conse- 

 quently, care should be taken to prevent this, as well as to 

 prevent the washing of the spores from field to field. Clean 

 culture and the deep burying or burning of all infested 

 plants is desirable. 



The Smut fungus apparently enters the seedling onions 

 about the time they come up, rather than later. Conse- 

 quently, onions started in special beds and transplanted are 

 seldom injured. 



OBSERVATIONS FOR PUPILS 

 Loose Smut of Oats 



1. Have you seen smutted oats heads in fields? How much damage 

 does the disease do in your neighborhood? 



2. If there is a compound microscope in school, examine the spores 

 under a high power. 



3. Bring in a diseased oats head which has not yet burst open ; place 

 the stem in a bottle of water and watch it for a few days to see the pro- 

 duction of spores. 



4. Make a sketch of a panicle of oats injured by Loose Smut. 

 J. Read Farmers' Bulletin 250. 



