January 24, i«95) 



NA TURE 



303 



that there was no increase in nitrogen during all the weeks 

 the Algae had been flourishing, and that accordingly no iota of 

 the stream of free nitrogen which had been consianlly passing 

 through the apparatus had lieen "fixed." So far, then, the 

 first Alga which had been put to the test of experiment showed 

 itself incapable of utilising atmospheric nitrogen. 



Kossowitch now turned to fresh expeiiments, choosing ^Igal 

 cultures of sometimes one, sometimes several species taken 

 together ; to all ol these he added simultaneously soil-barteria 

 of mixed sorts. The apparatus employed was very nearly the 

 same as that above descritjed. In these experiments he desired 

 to test the supposition of Berthelot and Winogradsky, who 

 considered the presence of certain organic substances to be 

 favourable to the fixation of nitrogen ; he accordingly arranged 

 his experiments in five pairs, both members of each couple 

 having identical conditions, except that in the one a small 

 quantity of sugar (dextrose) was added to the nutritive solution, 

 whilst in the other no organic compound was present. One set 

 was arranged with Cystococcus and soil-bacteria, and the results 

 obtained showed that in the absence of organic materials a 

 small but yet noticeable increase in the nitrogen of the system 

 had taken place (from 2'6 mg. to 3'i mg.) Where sugar had 

 been previously added, however, there were three times as much 

 nitrogen after the experiment as before. In a second pair of 

 cultures the Alga .Stichococcus and certain bacteria were used, 

 but here in no case, either with or without sugar, was there any 

 increase in nitrogen This shows that Stichococcus has in itself 

 no power of nitrogen fixation. 



Another couple contained a mixture of several Algae, Nostoc, 

 Cylindrospermuni, &c., and certain soil-bacteria. In this in- 

 stance a very large fixation of nitrogen took place, both where 

 sugar was present and where not ; in fact, in the former case 

 the nitrogen was increased more than nine-fold. 



All these observations shed much light upon the question of 

 the relations existing between .A-lgJe, micro-organisms, and 

 atmospheric nitrogen. They show: — 



(1) That at least two Algx — Cystococcus and Stichococcus — 

 possess no " fixing " powers in themselves. 



(2) That many .'\lgce, taken together with certain micro- 

 organisms of the soil, do possess the power of assimilating 

 atmospheric nitrogen. 



(3) That this power is much increased by the addition of such 

 organic suhstancesas sugar. 



It should be noticed that among the ten cultures used in the 

 second set of experiments, only two contained definitely isolated 

 algal species, viz. the cases of the two cultures of Cystococcus 

 and soil-bacteria. 



It was just in this instance, moreover, that it had been shown 

 that the Alga itself had no capacity for fixing atmospheric 

 nitrogen. Accordingly, there could be little doubt that it was 

 through the agency of the micro-organisms that the " fixation " 

 had taken place in these latter cultures. 



The experiments of Laurent and Schloesing had shown that 

 if in a culture of Alga; and bacteria endowed with "fixing" 

 powers, the AlgK were destroyed, the bacteria lost partly, if not 

 entirely, this capacity, which the mixture had possessed. This 

 pointed clearly to the fact that there was some close relationship 

 existing between the Alga; and micro-organisms. 



There are many facts which seem to indicate the nature of 

 this relationship. 



lierthelot found that the nitrification of the soil only look 

 place as long as organic compounds were present ; if these were 

 exhausted, the nitrifying process ceased. Gauiier an<l Drouin 

 also showed the importance which organic compounds have 

 with respect to nitrification. Kossowitsch's own experiments, 

 in which the advantage of adding sugar to the culture was 

 shown, also point in the same direction. 



From such observations as these, Kossowitsch concludes that 

 the relationship which the -Algx bear to the micro-organisms is 

 one connected with the organic foc<d supidy of these latter ; he 

 tliinks that the .'\lg:v, furnished with nitrogen by the bacteria, 

 i-similate carbohydrate material, part of which goes to their 

 own maintenance, but part also to that of the micro-organisms. 

 U is. therefore, in his belief, an instance of symbiosis in which 

 each supplies the wants of the other. There are many frets, 

 partly the result of his own o'lscrva^ions, partly the result of 

 those of others, which uphold this view. If the mixed culture 

 be placed in the light, there is a far more noticeable nitrogen 

 increase than when in darkness, .\gain, if a rich supply of 

 carbon dioxide gas be provided, this is marked by a decided rise 



NO 13 I 7, VOL. 51] 



in nitrogen-fixing powers. Both these conditions are such as 

 are known to influence carbohydrate assimilation in chloro- 

 phyll-containing organisms ; but all experience is antagonistic 

 to the view that light should be beneficial tothe vital activity of 

 the bacteria, and there are only one or two exceptional instances 

 (Nitromonas, &c.) in which carbon dioxide can be directly 

 assimilated by these micro-organisms. 



Moreover, in the cases where the bacteria are brought Into 

 immediate contact with the Alga, as in those species of .Algae 

 which are enveloped in a gelatinous covering wherein the micro- 

 organisms become embedded, nitrogen fixation appears to be 

 greatly aided, and the addition of sugar to the culture has no 

 such marked effect as in the instances where non-gelatinous 

 Algje are employed. The explanation of this seems to be that 

 the bacteria emijedded in the gelatinous sheath are amply pro- 

 vided with carbohydrate food without the addition of sugar, 

 which, therefore, comes more or less as a superfluity. 



All this seems to justify Kossowitsch's view of the part played 

 by the .K\^x in the fixation of nitrogen ; it appears to show that 

 they have an indirect, but none the less important, influence 

 upon the process. 



This is roughly the extent of Kossowitsch's article ; it has 

 been impossible to give here its details, the bare outlines of his 

 researches could alone be mentioned, but it is hoped that 

 sufficient has been said to show the importance of his work, 

 perhaps even to indicate the interest which every page of his 

 memoir possesses, dealing as it does with one of the most 

 fascinating branches of vegetable physiology. 



Rudolf Beer. 



THE COMMERCrAL SYNTHESIS OF 

 ILLUMINA TING H YD ROC A RBONS> 



'T'HE direct combination of carbon and hydrogen in the 

 ■'■ electric arc is a true case of synthesis, and if we could 

 form acetylene in this way in sufficiently large quantities, it 

 would be perfectly easy to build up from the acetylene the 

 whole of the other hydrocarbons which can be used for illu- 

 minating purposes. For instance, if acetylene be passed 

 through a tube heated to just visible redness, it is rapidly and 

 readily converted into benzol ; at a higher temperature naph- 

 thalene is produced, whilst by the action of nascent hydrogen 

 on acetylene, ethylene and ethane can be built up. From the 

 benzol we readily derive aniline, and the whole of that mag- 

 nificent series of colouring matters which have gladdened the 

 heart of the fair portion of the coaimunity during the past five- 

 and-twenty years, whilst the ethylene produced from acetylene 

 can be readily converted into ethyl alcohol, by consecutively 

 treating it with sulphuric acid and water, and from the alcohol, 

 again, an enormous number of other organic substances can be 

 produced, so that acetylene can, without exaggeration, he looked 

 upon as one of the great keystones of the organic edifice, and, 

 "iven a cheap and easy method of preparing it, it is hardly 

 possible to foresee the results which will be ultimately pro- 

 duced. 



In 1836, it was found that when making potassium, by dis- 

 tillation from potassic carbonate and carbon, small quantities of 

 a bye-product, consisting of a compound of potassium and 

 carbon, was produced, and that this was decomposed by water 

 with liberation of acetylene ; whilst Wiihler, by fusing an 

 alloy of zinc and calcium with carbon, made calcic carbide, and 

 used it as a source from which to obtain acetylene by the action 

 of water. 



Nothing more was done until 1892, when Macquenne pre- 

 pared barium carbide by heating at a high tempera'ure a mix- 

 ture of barium carbonate, powdered magnesium, and charcoal, 

 the resulting mass evolving acetylene, when treated with water ; 

 whilst, still later, Travers made calcic carbide by heating to- 

 gether calcic chloride, carbon, and sodium. None of these 

 processes, however, gave any commercial promise, as the 

 costly nature of the potassium, sodium, magnesium, or calcium- 

 zinc alloy which had to be used, made the acetylene produced 

 from the carbide too expensive. 



Whilst working with an electric furnace, and endeavouring 

 by its aid to form an alloy of calcium from some of its com- 

 pounds, Mr. T. L. Willson noticed that a mixture containing 

 lime and powdered anthracite, under the influence of the tem- 



1 Abstract of a paper by Prof. Vivian E. Lewes, read before ihe Society 

 of .^rts, Wednesday, Janii.iry 16. 



