AGRICULTURAL BOTANY. 625 



The role of nitrates in the nutrition of plants, E. Godlewski (Rev. Sci. 

 [Paris], IfO {1911). II, No. 6, p. US). — A note is given of investigations carried 

 on by the author in which wheat seedlings were placed in light and darkness 

 and grown in the absence of carbon dioxid in order to exclude the ordinary 

 phenomena of photosynthesis. One lot of the plants received calcium nitrate 

 and other mineral salts, while the others received the same mineral salts but 

 without any nitrogen. 



The plants which did not receive nitrogen lost a portion of their original 

 nitrogen, while those which had been given nitrates absorbed a considerable 

 proportion of the salt, forming nitrogenous compounds, and this took place in 

 darkness as well as in the light. The amid nitrogen was fouad to increase 

 much more abundantly in the plants which received nitrates than in those not 

 receiving these salts. The amids appear, therefore, not only as degradation 

 products of albuminoids, but also in the synthetic processes in the utilization 

 of nitrates. 



In the utilization of nitrogen by plants, the author states that there are two 

 stages, one which consists of a change from the nitric form to an amid form, 

 and the second where the amids are transformed into proteids. This stage is 

 little understood, but it was found not to take place except in the light, indicat- 

 ing that light is essential to albuminoid formation in plants. 



The utilization of cellobiose as a source of energy in nitrogen fixation 

 through bacteria, A. Koch and S. Seydel {CentM. Bakt. [etc.], 2. Abt., 31 

 (1911), No. 23-25, pp. 567-570). — Continuing investigations on nitrogen gain 

 and loss in soils (E. S. R., 23. pp. 122, 123, 429; 24, p. 140), the authors experi- 

 mented with solutions of cellobiose on agar, employing cultures of nitrogen- 

 fixing bacteria, both pure and mixed with other bacteria from the soil. 



In the case of the first there was no fixation of nitrogen, while in the latter 

 such fixation occurred. From this it appears, and is confirmed by later experi- 

 ments, that cellobiose is employed as a source of energy in nitrogen fixation, 

 not by the nitrogen bacteria directly, but after its being changed by the 

 agency of other bacteria, probably assisted in this case by the hydrolizing 

 action of Aspergillus niger. 



Investigations on the progress and economy of nitrogen fixation, A. Koch 

 and S. Seydel (CentU. Bakt. [etc.], 2. AM., 31 (1911), No. 23-25, pp. 570-577).— 

 Continuing the above studies on nitrogen fixation, the authors here undertook 

 to decide whether bacteria in taking nitrogen from the air employ all of the 

 energy used therewith, as, for example, tliat from the sugars, in building up 

 their own cell structures, or turn some of the supply to other processes, as the 

 building of reserve materials. With dextrose as a main source of energy the 

 authors carried out experiments for various periods of time, and then analyzed 

 the results for each period and calculated the number of milligrams of nitrogen 

 fixed per gram of dextrose used therein. 



Two facts were brought out, viz, (1) that as the experiment goes forward 

 and the increase of bacteria is checked the fixation of nitrogen per unit of 

 dextrose used decreases (presumably because the energy is turned to other pur- 

 poses), and (2) the cases of most rapidly increasing fixation show also the 

 highest rate of fixation per imit of the energy used, due probably to the very 

 rapid increase of bacteria. 



It is believed that the results point to a more rational and cheaper process 

 of nitrogen fixation in agricultural practice, as soon as a means may be found 

 to compel the bacteria to go on increasing at the rapid rate observed in the 

 earlier stages of the experiment, thus maintaining the high and profitable rate 

 of nitrogen fixation with the energy-giving material used. 



