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experiments we bad the root tubercles cut ofT, in otheivs tlie roots with 

 the tubercles were left united with large pieces of the stem, so that 

 eventually formed nitrogen compoiuids might be able to flow into 

 the stem. All our estimations, however, showed that not in a single 

 case the slightest fixation of nitrogen by the tubercles was obsei'vable. 

 As at first we doubted of the accuracy of oni* results obtained with 

 relatively little material, we afterwards used the just mentioned 

 larger t[uantities, but this did not make any difference either. Besides 

 the two said species we still exanjined several times 1Üto20grs. of 

 the nodules of Vicia faha, and once about 15 grs. nodules of 

 Rohinla pseudo-acacia, but other lesults were not obtained. 



As our researches did not last longer than 12 to 20 days it might 

 be objected that we have not sufficiently imitated the conditions of 

 the plants in the field. Further, that in these experiments the growth 

 of the tubercles, together with that of the whole plant, was excluded. 

 Although these objections have not been refuted in the preceding, 

 it is still highly improbable that nitrogen fixation would be associated 

 with the growth of the tubercles and not with the augmentation of 

 the Imcteria out of the jdant. Principal, however, is the fact that if 

 within the nodules nitrogen fixation were to take place, which might 

 have escaped our attention, the concerned quantity must certainly 

 be extremely small. When we now consider how difficult it is to 

 collect a few grams of tubercles for example of Rohlnia, it is clear 

 that if this material is to be of any significance for such a great 

 tree, its nitrogen-fixing power must be enormous. The experiments, 

 however, show that the tubercles are wholly inactive or nearly so, 

 hence there can be no question of attaching to them an}- importance 

 concerning the nitrogen nutrition, whilst yet nitrogen fixation by this 

 tree is as certain as for lupine and serradella and even on a much 

 larger scale. So the nitrogen nutrition of the Papilionaceae can 

 only be indirectly connected with the bacteria of the nodules. In 

 my opinion this relation can only exist in the herbaceous species 

 and in the germ plants of the shrubs and trees of that plant order, 

 but in full-grown specimens of the woody species such as Rohlnia 

 pseudo-acacia the presence or the absence of the nodules is wholly 

 indifferent. Likewise on the roots of shrubs, such as Sarotluimnus 

 vul(/(iris, Spartium scopariuni. Genista anglica, and Genista pilosa in 

 full-grown condition, the number of tubercles is so small, their 

 volume so insignificant to that of the whole plant, that even if they 

 were able to assimilate some free nitrogen their slight activity could 

 not possibly explain the rich nitrogen store of the whole plant. 



Hence, the at present generally accepted explanation of the peculiar 



