57 



compounds showed scarcely any advance in the young plants, while the plants in the pots with 

 nitrogen compounds matured daily more luxuriantly. After six weeks the contrast was as great 

 as possible. When no further advance in the development of the dwarfed plants without nitrogen 

 compounds could be observed, a correspondingly slight amount of nitrogen compounds was intro- 

 duced in the sand in the solution. Even in the next few days the effect was apparent. The little 

 plants developed further and. after the lapse of about three months, so far as their size, even if 

 dwarfed, permitted, the formation of blossoms could be recognized. When these had matured it 

 was shown that all experimental plants had become smutted, as might have been presupposed. 

 Also in the comparative series of experiments abundantly provided with nitrogen and in which 

 nitrogen compounds had also been added subsequently in order to cause the greatest possible 

 development, the plants did not remain in size much behind those in the open field and showed 

 in the inflorescence development of all individuals the most luxuriant formation of smut. By 

 means of photographic exposures (made by R. Scholz) the two parallel experiments of the 

 Sugar millet (Zuckerhirse) have been permanent and are reproduced in fig. i, plate 2, of this 

 volume. 



The result of the comparative experiments shows most conclusively that fungus threads 

 living parasitically, in this especial case, of smut fungi, are not able to bring about the provision 

 of their host plants with nitrogen from the air. Without nitrogen compounds, they soon stop 

 growth and resume the phenomenon only when further nitrogen compounds have been added. 

 From a comparison of the dwarfed plants without nitrogen compounds with the luxuriant normal 

 forms obtained by means of them, it is seen conclusively that filiform fungi, living parasitically 

 and concerned here, are not in a position to bring about an assimilation of free nitrogen even when 

 the most favorable objects are grown for the experiments. If assimilation of nitrogen cannot be 

 proven here, there is no great possibility that it can be the case in other fungi living para- 

 sitically. The somewhat quicker and more luxuriant development of host plants attacked by 

 fungi, mentioned above, must have other subsidiary causes which, however, in any case may not 

 be traced back to nitrogen assimilation. 



Experiments with these millet varieties were repeated in the course of three years and 

 always with similar results. Wheat and barley were used only later for the same experiments. 



Instead of young inoculated host plants, the experimental pots were sown with grain which 

 had been kept over from previous harvests, in which there had been a total infection of the 

 harvested grains. The experiments were set up and carried through in the same way as those 

 described above. During the period of experiment no disturbances whatever occurred and the 

 results were exactly the same as described for millet. The grain germinated into healthy seedlings, 

 which, lacking nitrogen compounds, stopped growing after all the reserve stuffs had been used 

 up. When in the course of three or four weeks this cessation of growth took place, the plants 

 were so benefited by a single addition of nitrogen compounds that they formed small inflor- 

 escences, which in every case were entirely Minuted. The comparative experiments with nitro- 

 gen compounds again gave a normal development of the plants and also the formation of com- 

 pletely matured smutted heads. By photographic exposures the actual condition was made 



