CORN SMUTS AND THEIR PROPAGATION 145 



diseased ears to healthy ones, and the ripening grains thus 

 actually infected look in the harvest apparently healthy. 

 They give, however, smutty plants the following season. Both 

 in barley and in wheat the smut mycelium has been found 

 in the apparently healthy grains of the artificially infected 

 flowers. There is thus no necessity here for the introduction 

 of any hypothesis such as the rust mycoplasm theory. Rather 

 the discovery of a definite smut mycelium tends to throw 

 further doubt on the possibility of the existence of the rust 

 mycoplasm. 



Another point of interest seems worthy of attention. At 

 one time the powdery smuts of wheat, barley, and oats were 

 regarded as one species, Ustilago Carbo. Twenty years ago 

 spore cultivation showed that the spores from these three hosts 

 did not behave alike. The oat smut spores sprouted quite 

 differently from the other two, and accordingly the oat smut was 

 called Ustilago Avence. The smut spores of barley and wheat 

 are indistinguishable in appearance, their mode of germination 

 is the same, and, in the opinion of Brefeld, they are one and the 

 same species. They are, however, now known as Ustilago Tritici, 

 Rostrup (wheat smut), and Ustilago Hordei, Bref. (barley smut). 



It would be a useful and interesting piece of work to test 

 how far they are species of distinct morphological value, or 

 if, being one morphological species, they are biologic forms or 

 species. I am not aware that any attempts at infection of wheat 

 plants by barley rust or the converse have been made. The 

 matter is of sufficient biological and practical interest to deserve 

 experimental attention. 



From what has already been said, it follows that in wheat 

 and barley the danger of infection of seedlings from smut spores 

 in the soil or clinging to the grains is slight or non-existent, 

 and that grain treatment by fungicides is valueless. It is 

 impossible to pluck out of an infected field the diseased plants, 

 so that the farmer should, as far as possible, use for sowing 

 purposes grain coming only from fields known or guaranteed to 

 be smut free. Soaking with fungicides of wheat or barley grains 

 harbouring the smut mycelium does not reach the mycelium, 

 and the death of the adherent smut spores is objectless, as they 

 are harmless. 



Oat smut is in its general characters like barley or wheat 

 smut ; its spores, too, are, as seen microscopically, similar. 



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