6?o How Cereals are Infected with " Smut." [feb., 



during the flowering stage. Plants that have been infected 

 during the seedling stage can often be recognised by an expert 

 by their more robust growth and darker green colour, the 

 presence of the fungus in their tissues stimulating the plant to 

 more active growth. As a result, such diseased plants are often 

 taller than non-infected ones, and mature somewhat earlier, the 

 "smut " spores being ripe and dispersed just at the time when 

 uninfected plants are in flower. 



No practical method suggests itself for the prevention of infec- 

 tion through the flowers. 



A thorough reinvestigation of the whole subject of infection 

 and transmission of " smut " disease in cereals must now be 

 undertaken, as the recent discovery suggests certain possibilities 

 or even probabilities. 



Recent research has indicated that in the case of some of our 

 most destructive diseases, mycelium of the fungus hibernating 

 in the tissues of reproductive portions of plants is a more con- 

 stant and certain method of perpetuating a disease than by 

 means of spores. As examples : mycelium in the tuber causes 

 potato blight and leaf-curl ; in branches, causes peach leaf- 

 curl ; in rhizomes, curl disease of mint, " smut " in reeds, &c. ; in 

 seeds, the infected grain of various species of rye-grass, &c. 



It has now to be definitely determined whether the mycelium 

 formed in a barley grain always produces " smut " spores during 

 the season of infection, or whether the mycelium remains 

 passive until the seed is sown, when it would pass into the 

 seedling, grow up along with it, and finally form spores in the 

 grain. 



The frequent appearance of a considerable percentage of 

 " smutted " ears in a crop after the seed had been specially 

 treated with a fungicide suggests the probability of some other 

 means of perpetuating the disease than by infection of seedlings 

 by spores present in the soil. 



Suggestions for the prevention of "Bunt and Smut" are 

 given in Leaflet No. 92, while references to the use of formalin 

 as a preventive have appeared in this Journal, Vol. IX., p. 366, 

 Dec, 1902; Vol. XL, p. 215, July, 1904; and to the effect 

 of formalin and blue-stone on germination in Vol. XIL, p. 289, 

 August, 1905. 



