55 



OF THE ASSIMILATION OF NITROGEN'. 



Tn the inoculation of blossoms with the loose smut of barley and of wheat it has been 

 proved possible to harvest grain which after sowing gave total infection of all plants under 

 experimentation. In the same way in the smut of Indian millet, Panicum and Italian millet, a 

 total infection of the plants under experimentation was obtained, if the germinating seedlings 

 were inoculated sufficiently carefully Ijy means of an atomizer. We have accordingly in the 

 host ])lants of the smut fungi here named material which will lead with perfect certainty to the 

 formation of smutted plants. 



With this material it has now been possible to decide definitely a physiological question 

 of especial interest ; namely, the (|ucstion as to a possible assimilation of free nitrogen by the 

 fungus mycelia which live parasiticalU' in their host plants. This question became of importance 

 through the excellent investigations of Hcllric tjcl, which prove definitely that lupines and other 

 Leguminoseae can live in soil without combined nitrogen, that is, chemical compounds of nitro- 

 gen, and are able to assimilate the free nitrogen of the atmosphere, if they are inhabited by para- 

 sitic fungi. Hc!lric(/cl succeeded in Ijringing the above-named Leguminoseae to full development 

 in pure vitreous sand, which had l)een provided with mineral salts in solution, but remained free 

 from combined nitrogen, if definite forms of bacteria rhizobia could attack the roots of these 

 host plants and produce tuber-like swellings there. 



The fortunate results of Hcllricgcl's cultures have brought forward the question whether 

 other fungi living parasitically in their host plants can cause a similar assimilation of free nitro- 

 gen. A series of iilienoniena, for instance, mycorhiza, which occur universally distributed on 

 the roots of different plants, favors its explanation in this way. Experiments were made with 

 tree-like plants several years old, in which it was thought possible to prove that the mycorhiza 

 living on the roots can cause assimilation of free nitrogen. Experimental material in perennial, 

 slowlv growing plants, said to assimilate uncombined nitrogen, does not promote, however, the 

 decision of this question as to the assimilation of free nitrogen. In time, unavoidable sources 

 of error creep into experiments with perennial plants, which offer no security for a scientifi- 

 cally certain result. Experiments of this kind can be carried through successfully only with 

 quickly growing and large annual plants through which the proper parasitic fungi grow, from 

 germination to the end of development, and which attain the most luxuriant development pos- 

 sible. In this kind of experimental object, it must be assumed that parasites of these plants 

 living saprophvtically do not cause the least damage and that some connection exists between 

 the parasites and the host plants, as was found in the Leguminoseae and their rhizobia. Experi- 

 mental objects of the necessary and desired kind are furnished now in an absolutely ideal form 

 in our large annual grain species which smut fungi attack and in which they live. In one 

 vegetation period a plant attains its complete size and maturity. The parasite penetrates into 



(1) A preliminary report on this subject has been published in a lecture before the Schles. Gesell- 

 schaft fur vaterliindische Cultur, on the 15th of November, 1900. 



