21 



takes place in the blossom. A summary of the experiments thus carried out is added in small 

 print at the end of this section. 



Hence it is proved positively that young ovaries are directly attacked on their stigma^by 

 the germs of infection scattered by the uind; that the smut, hoivever, is not developed in the 

 same year; but that rather the germs of infection which penetrated into the young embryonic 

 fruit remain latent in the ripened grain and after the dormant period of the seed grow out in 

 these, equally, with the germination of the embryo, in order to pass over in the inflorescence to 

 the production of the spore masses. 



The seed from cylinder infection was treated in the same way. The percentage of smut- 

 ted plants fluctuated between i8 and 26 per cent. In the survey at the end of the section, the 

 details are summarized in small print from the list of experiments which we made. 



The seed harvested in the separate experimental infections was not used up entirely in 

 the experiments, but a part was always kept over in order to answer any subsequent questions. 

 The seed, obtained in autumn from a complete infection of the experimental plants, was inves- 

 tigated first of all microscopically, in order to prove the presence of fungus germs in the grains. 

 This was done without any difficulty. Mycelial threads of the fungus were found in different 

 parts of the grain, especially underneath the gluten cells. They were especially present near the 

 scutellum. In the germinating seedling, the fungus threads were more clearly distinguishable, 

 since the grain attacked by them and sterilized had been sown, and fungus threads appeared 

 clearly in the tissue cells in all parts of the sprouting embryo, from the scutellum to the vege-/ 

 tative tip. Accordingly no doubt can exist that the germs of infection, which had penetrated 

 into the young ovary, had remained in a purely vegetative condition here and had passed through 

 the dormant period of the seed. They awoke to new life simultaneously with the sprouting 

 germinating seedling and developed equally with this, as it grew into the mature plant. Here 

 it formed anew its spore masses in the inflorescences. Only the threads of the fungus whiih 

 reached the vegetative tip of the plant with its embryonic inflorescences become fertile at this 

 point and form spore masses. The mycelial threads in all other parts of the plant remain sterile 

 without fructifying. They are widely separated from one another by the growth of the plant 

 and are found with difficulty in the elongated internodes, but very easily in the cells of the nodes, 

 which are often completely filled with them*. It is possible for them to redevelop and to cause 

 disease in the axillary sprouts only in those cases where such sprouts are formed on the nodes, 

 and young tissues are developed^ 



Such are the results of blossom infection by the loose smut of wheat, in contrast to which 

 we must now place the results of infection on the germinating seedlings of the young seed. Infec- 

 tion of the young germinating seedlings was tried in four different ways as stated above. First 

 the grain was mixed with smut spores and then sown directly upon the land. The infectious 

 action of the smut spores clinging to the grains had to take effect here. In the second case the 

 young germinating seedlings were sprayed with spores which had been purified and then prepared 

 for germination in diluted nutrient solution. Here the contact of the germinating tubes, growing 



(1) Compare illustration 7 on the first plate in Part XI. 



(2) Compare text in Part XI, pages 85-90. 



