CEREALS 345 



in Kansas, found different fields to have 8, 15.3, and 18.3 

 per cent of smut, while single portions of a field showed as 

 high as 39 per cent. The annual loss in this country is 

 somewhere between $10,000,000 and $20,000,000. 



The reasons for underestimation of oat smut are the 

 dwarfing of many of the affected plants: which thus re- 

 main unnoticed by a casual glance over the field, and the 

 fact that many smutted panicles remain invisible unless 

 unrolled from their enveloping leaves. 



It was proved as early as 1858 that infection can occur 

 only upon the very young oat plant: that older plants 

 are immune. It was later determined by Brefeld that 

 the plants are immune after the leaves have protruded 

 1 cm. beyond the leaf sheath. From this it follows that 

 the chief (and as other experiments have demonstrated 

 practically the only) infection comes from smut spores 

 which are upon the seeds when they are planted. These 

 sprout, producing sporidia which infect the young plant. 

 The fungus develops in these plants throughout the 

 season without conspicuous effect until, at blossoming 

 time, the fungus seeks the ovaries and the glumes and ap- 

 pears again as the famihar black spore masses. 



Any treatment which kills the spores upon the seed with- 

 out materially injuring the seed itself results in a clean crop. 



The bluestone treatment so widely used to prevent wheat 

 smut, however, is not advisable for oats, since its use is at- 

 tended with too much danger to the germinating power of 

 the oat seed. The hot-water treatment as appHed to wheat 

 for loose smut, using a temperature of 132°-133° F. for 

 ten minutes, 130° F. for fifteen minutes, or 145° F. for not 

 more than five minutes, may be employed with perfect 



