1890.] On the Question of the Fixation of Free Nitrogen. 99 



percentage of nitrogen in the dry substance, of both the above- 

 ground and the nnder-gronnd produce, is lower than in either of the 

 other cases. It may be further noted, that the roots grown in pots 2 

 and 3 with the soil-extract, and with so much greater development of 

 nodules than in either pots 1 or 4, at the same time contained a con- 

 siderably higher percentage of nitrogen in their dry substance. 



The next table shows the actual quantities of dry substance, of 

 ash, and of nitrogen, in the separated, and in the total, products of 

 growth. 



Actual amounts in the produce. 





Dry substance. 



Ash. 



Nitrogen. 



In 



stems 

 and 

 leaves. 



In 

 roots. 



In 



whole 

 plant. 



In 



stems 

 and 

 leaves. 



In 



roots. 



gram. 

 0-745 

 0-885 

 0-407 

 -582 



In 



whole 

 plant. 



In 



stems 

 and 

 leaves. 



In 



roots. 



In 

 whole 

 plant. 



Pot 1 



Pot 2 



Pot 3 



Pot 4 



grams. 

 7-423 

 9-368 

 9-411 



12 -808 



. grams. 

 2-600 

 2-409 



1- 748 



2- 846 



grams. 



10 -023 



11 -777 

 11-159 

 15-654 



grams. 

 1 -462 

 1-505 

 1-305 

 1-175 



grams. 

 2-207 

 2 -390 

 1-712 

 1-757 



gram. 

 0-2153 

 0-4591 

 0-3771 

 0-5816 



gram. 

 0-06H9 

 0-0770 

 0-0587 

 0-0794 



gram. 

 2822 

 0-5361 

 -4357 

 -6600 



It is seen that there is more dry substance in the above-ground 

 growth, but less remaining in the roots, in pots 2 and 3 with the soil- 

 extract than in pot 1 without it. In the whole plant there is, of dry 

 substance with soil-extract, about llf grams in pot 2, and more than 

 11 grams in pot 3, against only 10 grams in pot 1 without soil- 

 extract. 



The point of chief interest is, however, that there was twice, or 

 more than twice, as much nitrogen in the above-ground growth in 

 pots 2 and 3 with the soil-extract seeding, as in pot 1 without it. But 

 there is much less difference in the amount of nitrogen remaining in 

 the roots under the different conditions. In the total vegetable matter 

 there is in pot 2 more than twice, and in pot 3 nearly twice, as much 

 nitrogen as in pot 1 without the soil-extract. 



With the full supply of already combined nitrogen in pot 4, with 

 garden soil, there was about one and a third time as much dry sub- 

 stance produced, and more nitrogen assimilated, than under the 

 influence of the soil-extract seeding. 



The significance of the results relating to the nitrogen is, how- 

 ever, more clearly brought to view in the next table, which shows — 

 the amounts in the soils at the commencement and at the conclusion 

 of the experiment, and the gain or loss ; the amounts in the seed, in 

 the total products of growth, and the gain ; the total nitrogen in the 



VOL. XLV1I. i 



