October 13, 1892] 



NATURE 



579 



Organ'sms by whose Activity the Snl is Enriched in Nilrogin. 

 A distinctioa must he drawn between the higher and lower 

 plants. It IS a well-known fact that most plants cannot assimi- 

 late free nitrogen ; whereas there are sound reasons for the 

 helief that the legumes are exceptions to this rule. The expla- 

 nation has been sought in the tubercles. These tubercles con- 

 tain a tissue, consisting of thin-walled cells filled with an 

 albuminous substance, consequently they are richer in nitrogen 

 than the roots ; they have been regarded by some as pathogenic 

 {growths, by others as reserve reservoirs for albumin. We may 

 now conscientiously assume that these tubercles arise through 

 exterior infection, and that they are not normal growths. 



Hellriegel and Wilfarth,' in their great work, state:— "The 

 legumes deport themselves quite difterently from the non-legumi- 

 nous plants respecting the assimilation of nitrogen, whereas the 

 latter are totally dependent for their nitrogen needs upon the 

 nitrogen compounds present in the soil, and their development 

 proportional to such disposable supply. The legumes have, be- 

 sides, the soil nitrogen, a second source, from which they can 

 abundantly cover any deficiency existing in the first. This second 

 source is free atmospheric nitrogen. The legumes attain this 

 power by the co-operation of active living micro-organisms. The 

 mere presence of low organisms in the soil does not suffice to 

 niake the free nitrogen serviceable, but it is necessary that certain 

 kmds of organisms enter into a symbiotic relationship with the 

 legumes. 



Lupines acquire nitrogen like the other legumes. They 

 starve in a soil free from nitrogen when the presence of low 

 organisms is excluded ; but when this is not the case their 

 growth is normal. The experiments were carried on in sand 

 containing a suitable nutritive solution. Some of the pots were 

 sterilized ; to some infusions from soil were added. In all and 

 in only those, to which fresh infusions of lupine soil had been 

 added the lupines developed normally bearing the well-known 

 tubercles on their roots, and contained, when harvested, con- 

 spicuously larger amounts of nitrogen than the soil and infusion 

 could have given them. Wherever the infusion had not been 

 added, or where it had been sterilized at loo or even 70, the 

 development remained abnormal, the production scant ; tubercles 

 remained absent and the harvested plants contained less nitrogen 

 than had been offered them. 



According to Ward,-' Breal,^ and Pradmowski,* tubercles 

 will grow on plants free from them when infected with an 

 infusion from tubercles of other plants. 



Beyrenick '•" has named the infecting organisms, of which there 

 may be many varieties. Bacterium Radicola, With the growth 

 of the tubercles the behaviour of the plant towards nitrogen is 

 changed, and the just mentioned independence begins ; this has 

 been proved by an almost superabundance of experiments. 

 Still the explanation of the manner in which the nitrogen is 

 acquired is not definitely settled. The first inference would be 

 that the root-inhabiting bacteria possess the power of assimilating 

 atmospheric nitrogen, and the higher plants as hosts harbouring 

 these bacteria in their roots, use the nitrogen compounds so 

 produced. Thus there would exist a case of symbiosis between 

 Split Fungi and the higher plants. We cannot be too slow in 

 accepting this seemingly simple explanation — still the difficulty 

 of a correct interpretation does not alter the fact that the legumes 

 acquire free nitrogen from the atmosphere, and that the refuse 

 of their roots thus enrich the soil. They may be called nitrogen 

 collectors in contradistinction to the graminaceous nitrogen con- 

 sumers. 



Berthelot " has long contended that the free soil can fixate 

 nitrogen ; he considers a sandy and clayey nature of the soil 

 essential, it must admit of free access of air, must not be too 

 moist, be rich in potash and. poor in nitrogen. Gautier and 

 Drouin "^ claim that the presence of humous substances causes 

 increase of nitrogen. 



Soils free from organic substances do not fixate nitrogen, or 

 the gain is slight. The presence of ferric oxide so long con- 

 sidered capable of fixing nitrogen, has no effect. Berthelot, as 

 well as most investigators in this line, attribute the fixation to 

 the activity of nitrogen fixing chlorophyll free bacteria. In 

 most casas the amount is much less than that obtained in soils 

 with legumes. No inorganic soil constituents are known to 



' Z. Rub., XXV. I. 234. 2 Bied. Cent., BL, xvi. 787. 



3 Cr. cvii. 397. 4 N. Rd., iv. 201. 



5 Boh atg,, xlvi. 725, 741, 757, 781, 797. 



6 Cr. evil. 207, 852 ; cvi. 638, 1049, 1214. ^ Cvi. 754, 944, T098, 1174. 



NO. II 98, VOL. 46] 



possess the power of fixing nitrogen, and it is questionable 

 whether humous substances can directly do this. 



In 1881 Atwater claimed ■ that peas during their growth 

 obtamed large quantities of nitrogen from the air. Atwater ' 

 and Woods made another series of eighty-nine experiments ; the 

 result will be found in their admirable paper in the American 

 journal. I will quote the following: "There was in no case 

 any large gain without root tubercles ; but with them there was 

 uniformly more or less gain of nitrogen from the air. As a 

 rule, the greater the abundance of root tubercles, the larger and 

 more vigorous were the plants, and the greater was the amount 

 of atmospheric nitrogen acquired. The connection between the 

 root tubercles and the acquisition of nitrogen, which was first 

 pointed out by Hellriegel, is abundantly confirmed. In a 

 j number of these experiments, there was a loss of nitrogen in- 

 I stead of a gain. The loss occurred where there were no root 

 tubercles ; it was especially large with oat and corn plants, and 

 j largest where they had the most nitrogen at their disposal in the 

 form of nitrates. This loss may probably be due to the decom- 

 position of the seeds and nitraces through the agency of micro- 

 organisms. In brief, the acquisition of large quantities of 

 atmospheric nitrogen by leguminous plants, which was first 

 demonstrated by experiments here, and has been since confirmed 

 by others is still further confirmed by the experiments herewith 

 reported. These experiments in like manner confirm the ob- 

 servation of the connection between root tubercles and the 

 acquisition of nitrogen. There is scarcely room for doubt that 

 the free nitrogen of the air is thus acquired by plants." 



Chemists, as a rule, hesitate to accept isolated cell life as 

 modifying and conditioning the action of those more differ- 

 entiated ; yet it seems that all circumstances point to the fact 

 that most reactions taking place between nitrogen and plants 

 are influenced by micro-organisms. 



Let us hope that chemistry will, in the near future, score its 

 greatest agricultural triumph, by unveiling the mysteries which 

 still shroud the specific actions of these organisms, thus making 

 it possible to supply the demands of a constantly increasing 

 population. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Cambridge. — A course of instruction (Lectures anc 

 Laboratory work) in sciences bearing upon Agriculture will be 

 commenced in Cambridge this term ; it will extend over two 

 years and will include the following subjects :— Agriculture ; 

 Chemistry, elementary and agricultural ; Botany, elementary 

 ! and agricultural ; some departments of Physiology and Geology ; 

 Agricultural Engineering, Surveying, and Mensuration. 

 Arrangements will also be made for instruction in Book-keeping, 

 and in Agricultural Law for those who desire it. The subjects 

 taken this term will be Elementary Chemistry, by Prof. 

 Liveing ; and Elementary Botany, by Mr. Seward, of St. 

 John's College. It is hoped that this course will prove useful 

 to gentlemen intending to farm, or to manage their own land, 

 and to those who are likely to become estate agents. Further 

 information may be obtained from Mr. H. Robinson, at the 

 University Chemical Laboratory, Cambridge Prof. Foster 

 announces a new intermediate course in Physiology, with 

 laboratory work, especially for medical students, to be given by 

 Dr. L. E. Shore, on Wednesdays and Fridays at ten, during the 

 Michaelmas and Lent terms. 



Dr. Donald Macalister, St John's, has been appointed Assesf or 

 to the Regius Professor of Physic. 



Mr. S. F. Dufton has been elected to a Fellowship at Trinity 

 College, and Mr. A. Hutchinson of Christ's has been elected to 

 a Fellowship at Pembroke College, in each case for distinc- 

 tion in Chemistry. Both gentlemen took first classes in each 

 part of the Natural Sciences Tripos. 



Mr. J. Y. Buchanan, F.R.S., University Lecturer in Geo- 

 graphy will deliver a course of lectures on Oceanography during 

 the present Term in the New Museums, on Tuesdays it 12 

 o'clock, commencing on Tuesday, October i8. 



Mr. W. C. D. Whetham, B.A., Fellow of Trinity College, has 

 been appointed Assistant Demonstrator of Physics in the Caven- 

 dish Laboratory. 



Mr. W. B. Hardy,M A., Junior Demonstrator of Physiology, 

 has been elected to a Drosier Fellowship in Gonville and Caius 

 College. 



Amer.Cheiii. Jour., xii. 526 ; tiii. 4a. 



