20 



In this cylinder infection also the appearance of smut never showed in the grain heads 

 harvested in the autumn. The harvested grains preserved with the precautions already given 

 had a perfectly healthy and normal appearance. These experiments were carried out principally 

 on summer wheat; less often on winter wheat, as is shown in the following statistics. 



The grains, harvested from infection of separate blossoms and from cylinder infection 

 and especially taken from different varieties of wheat, were sown in the following spring. This 

 was done with precautions which excluded all chances of error. The grains were sterilized with 

 copper sulphate solution according to Kuhn's process 1 in order to kill all smut spores which might 

 be present on the outer surface. That this actually took place was proved by special experiments 

 in which smut spores were treated according to the same process and at the same period with 

 the same copper solution. After thorough purification they were tested in nutrient solution as to 

 their capacity for germination. When the outer surface had thus been sterilized, the grains were 

 sown in special germinating cases, a suitable distance apart. Each germinating case held about 

 300 grains. The single grains lay free on a substratum of sterilized vitreous sand, which cov- 

 ered the underlying substratum, i-2cm thick. The germinating cases were covered and put in a 

 cool place, the germination of the grain was watched. When the sprouting seed had grown pos- 

 sibly 2cm out of the sheath, the cultures were put in the open air in a protected place and then 

 transplanted singly to the experimental beds in the open ground. It is impossible in this kind of 

 treatment for any infection germs to penetrate from without to the young plants. The plants 

 are immune, if the seedlings have grown 2-3011 out of the sheath, as had been proved earlier 

 for sorghum 2 , the first green leaves having appeared. In this condition, assured against all 

 external attack of fungus germs, they are planted in the open ground, where they need protec- 

 tion only from frost and other injurious natural conditions. The plants already set out developed 

 in different years quite normally, just as did the remaining grain plants in the fields. They 

 seemed externally perfectly healthy and did not show a trace of disease. Only at the beginning 

 of the blossoming time were results of the previous infection to be seen in places where the 

 embryonic heads grow out of the tips of the surrounding embryonic leaves. These results are 

 summarized in the following tabulated survey. It is necessary here to emphasize only the fact 

 that in the experiments of a separate infection of the blossoms, the damaging smut increased up 

 to 100 per cent. The appearance offered by these smutted fields was very phenomenal ; for the 

 experimenter indeed a very enchanting picture, because it proves the success of his tiresome 

 experiments and the correctness of the train of thought previously carried out. Never indeed 

 have such smutted fields been seen, as shown for example in the photographic picture of 

 wheat, fig. 2, plate I, which proves a total infection of all the experimental plants. If in the 

 separate experiments all the plants did not become smutted, it may be traced back to the 

 sources of error already indicated which are unavoidably present in experimentation. But even 

 such fields, in which 5-7 P er cent of smutted plants may be counted, give sure and unassail- 

 able proof of the correctness of the decision that here, in the loose smut of wheat, infection 



(1) After treating 12 hours with 5 per cent coppersulfat solution at 15-20 degrees C., the seed 

 was washed, let stand five minutes in fresh lime water, washed again and then sown directly on the land. 



(2) Compare the text in Part XI. 



