George Raymond Gage 13 



in petri dishes and inoculated them with spores. When mycelium had 

 developed he inserted these pieces of glumes between the glumes of his 

 seed oats. This was the method previously mentioned as being suggested 

 by Zade. The highest percentage of infection resulting from the oats 

 which were inoculated in this way was 26.4 per cent. In most of the 

 varieties tested the average percentage of resulting smutted plants was 

 less than 6 per cent. 



COMMENTS ON THE LEIPZIG INVESTIGATIONS 



The most outstanding contribution to our knowledge of the life history 

 of Ustilago avenae since the pioneer investigations of Brefelcl. Jensen, 

 and Kellerman and Swingle, at least in the writer's opinion, has been 

 this discovery of spore germination at blossoming time by Zade and his 

 students. Bref eld's successful but artificial method of spraying young 

 seedlings with sporidia grown in artificial culture was accepted as final 

 confirmation of the conclusions of Kiihn and Wolff in regard to the pri- 

 mary nature of seedling infection. The recent discovery of immediate 

 spore germination has opened again what has been considered a closed 

 chapter, and has especially stimulated the writer to seek further en- 

 lightenment on the life histories of the oat-smut pathogenes. 



It may be recalled that Zade, Neumeyer, Arlancl, Diehl, and Roesch 

 worked only with U. avenae. The life history of U. levis also needs in- 

 vestigation. Furthermore, it may be concluded that these German 

 workers consider the mycelium and the gemmae in the glumes, and pos- 

 sibly in the stigma and anther remains, to be the chief inoculum for 

 seedling invasion. Certainly they do not consider the mycelium in the 

 epidermis of the caryopsis pericarp as being especially significant. Zade 

 stated in his first paper (1922) that he would undertake to sow oats 

 from artificially inoculated blossoms, of which part would be glumed 

 and part deglumed. If his assumptions were correct, infected oat plants 

 should come from the glumed oats, while the deglumed oats should give 

 rise to healthy plants. So far this has not been reported as carried out. 

 In his second paper, it will be remembered, he says that he suggested a 

 method to Roesch whereby the glumes of oats might be inoculated and 

 become infected. This method has been described in the discussion of 

 Roesch 's studies. Zade predicted that the stands of plants coming from 

 such inoculated seed would show whether the resting mycelium and the 

 gemmae in the glumes were really the true inoculum for seedling in- 

 vasion, a theory which thus far had only been assumed. It will also be 

 remembered that Roesch 's results show a maximum percentage of 26.4 

 per cent of smutted plants, which was an exception to the general aver- 

 age of less than 6 per cent. In Zade's first paper he states that the 

 26.9 per cent of smut obtained by dusting spores on deglumed kernels is 



