No. 1071, Vol. 42] 



NA TURE 



41 



they are of saleable size ; or, to carry the process a step further, 

 the larvjE reared in hatcheries may be turned into similar ponds 

 and brought to maturity. These operations have been conducted 

 with success in more places than one, but the only places where 

 marine fish-culture forms an industry of any importance is in 

 the Adriatic, where there are large inclosures known as valli, in 

 which young fry, caught in the open sea, are inclosed and brought 

 to a marketable condition. The possibility of cultivating mus- 

 sels and oysters in the like manner is too well known to require 

 further mention, and it is quite possible that it may be found 

 practicable to apply the system of culture to lobsters. 



These are the practical questions to which fishery officers will 

 have to turn their attention. That a preliminary scientific train- 

 ing is necessary is obvious, for the art of culture requires the 

 most exact knowledge possible of the animals under cultivation, 

 and success will in each case depend on the extent to which the 

 necessities of the organism are studied and supplied. But ab- 

 stract scientific study must give way to practice ; as soon as a 

 man allows the problems of morphology and phylogeny to 

 distract his attention, he will become less careful of his prac- 

 tical experiments, and they will end in disappointment. The 

 Scotch Fishery Board has made an excellent beginning in its 

 trawling experiments ; in a short time it may be hoped that its 

 staff will be engaged in numerous other experiments on the pro- 

 tection and production of fishes, Crustacea, and mollusks, to 

 which many of the observations published in the Seventh Report 

 are but the preliminary. G. C. B. 



THE FIX A TION OF FREE NITROGEN} 

 TN a paper communicated to the Royal Society ia 1887-88 

 (Phil. Trans., 1889), the authors di>cussed the history and 

 present position of the question of the sources of the nitrogen of 

 vegetation. The earlier results obtained at Rothamsted, as well 

 as those of Boussingault, under conditions in which the action 

 both of electricity and of microbes was excluded, led the authors 

 to conclude that the higher chlorophyllous plants have not the 

 power of taking up elementary nitrogen by means of their leaves, 

 or otherwise. The conclusions arrived at were, that atmo- 

 spheric nitrogen is not a source of nitrogen in the case of 

 gramineous, cruciferous, chenopodiaceous, or solaneous crops, but 

 with regard to the Leoumiiiosir it was admitted that there was 

 not sufficient evidence to account for the whole of the nitrogen 

 taken up. Of the recent researches bearing on the subject, those 

 of Hellriegel and Wilfarth, first published in 1886, were con- 

 sidered the most striking and conclusive. 



In 1883, Hellriegel grew plants of various families in washed 

 sand containing the necessary ash constituents but no nitrogen ; 

 in one series nothing further was given, whilst to others varying 

 known amounts of sodium nitrate were added. The gramineous 

 and some other plants of the first series were all limited in 

 growth by the amount of nitrogen contained in the seed, and in 

 the other series the growth was largely proportional to the 

 amount of nitrogen which was applied. On the other hand, 

 whilst most of the peas of the series to which no nitrogen was 

 added failed after a short time, some would develop luxuriantly ; 

 and it was found that the roots of the plants of limited growth 

 were free from nodules, and that there was abundant nodule for- 

 mation on the roots of the well-developed plants. These results 

 led Hellriegel to make further experiments, the results of which 

 showed that leguminous plants will not develop to any extent in 

 sterilized sand free from nitrogen ; whilst in the case of peas, 

 vetche?, and some other Papilionacecc, the addition of a small 

 quantity of soil extract containing an immaterial amount of 

 nitrogen, causes the plants to grow luxuriantly. A soil extract, 

 prepared from an ordinary soil, which produces such striking 

 results with the plants just mentioned has no effect with lupins. 

 The same result is, however, readily obtained with lupins by the 

 application of a soil extract from a sandy soil in which lupins 

 have been growing. With clover less definite results were ob- 

 tained for some time, but more recently it has been observed 

 that whilst the extracts from other soils produce little or no 

 effect on clover, an extract from a root-crop soil brought about 

 a considerable nitrogen fixation ; but the result was less marked 

 than with iheothtr leguminous plants. In all cases the nitrogen 

 i-<imilation was accompanied by nodule formation on the roots, 

 rilizedsoil extracts were entirely without effect. 



■' New Experiments on the Question of the Fixation of Free Nitrogen 

 ( I'reliminary Notice)," by -Sir J. B. Lawes, Bart., LL 1)., F.R.S., anJ Prof. 

 J. H. Gilbert, LL.D., F.R.S. (Proc. Roy. Soc, xlv.i. 85). 



As stated in a postscript to the paper in the Phil. Trans, 

 already referred to, a preliminary series of pot experiments on 

 similar lines to Hellriegel's was commenced at Rothamsted in 

 1888. The plants selected were peas, blue lupins, and yellow 

 lupins. They were grown in washed sand containing a small 

 amount (00027 per cent.) of nitrogen and the necessary ash 

 constituents ; whilst for comparison all the plants were grown in 

 a rich garden soil, and the lupins in a special lupin soil as well. 

 As more normal and satisfactory growth was obtained with peas, 

 only the results relating to these will be discussed here. The 

 lupins, which are admittedly difficult to manage under the 

 artificial conditions which must, more or less, prevail in experi- 

 ments of this kind, gave no very definite indications in the first 

 year's experiments, although, in 1889, the most striking of the 

 results were those obtained with yellow lupins. Of the peas 

 grown in sand. No. i had nothing further added, whilst to Nos. 

 2 and 3 an extract from the garden soil was added. All the peas 

 germinated and grew well, but about five or six weeks after 

 sowing, the plants of the pots seeded with soil organisms began 

 to acquire a darker colour than those of the pot which was not 

 so seeded, and from this time the plants gained both in leaf 

 surface, and in number of leaflets, and maintained a brighter 

 green colour. At the conclusion of the experiments it was found 

 that the roots of the plants in the unseeded pot had many 

 nodules ; the roots of the plants of the seeded pots had many 

 more and much larger nodules than those of the unseeded pot. 

 That these had nodules at all is to be attributed to the impurity 

 and non-sterilization of the sand. The root, too, was much more 

 distributed through the whole of the sand which was seeded 

 than through the sand which was not seeded. The roots of the 

 plants grown in garden soil were very much developed, but 

 showed comparatively few nodules, which were, moreover, 

 smaller than those of the other pots. Owing to the lateness of 

 the season none of the plants flowered. 



With regard to the above ground growth at the end of the 

 experiment, there was more vegetable substance produced in the 

 pots seeded with soil organisms than in the unseeded pot ; and 

 this increased growth was without doubt connected with the 

 development of the root nodules and their contents. But the 

 greatest gain was in the total nitrogen. In fact, whilst the 

 amount of dry produce in the seeded pots was less than one-fifth 

 more than that of the unseeded pot, there was about twice as 

 much nitrogen in the above ground growth of the seeded, as in 

 that of the unseeded pot. In the case of the garden soil there 

 was more growth, more dry substance, and more nitrogen than 

 in any of the others. In all three pots with sand, the amount of 

 nitrogen in the produce, and in the sand, at the end of the ex- 

 periment was far greater than that of the seed sown, and the sand, 

 at the commencement. In each case the amount of nitrogen in the 

 sand remained practically unchanged, the gain, therefore, being 

 in the plants. The same may be said of the garden soil, but 

 with some reserve, owing to the great difficulty, to say the least, 

 of detecting slight changes in the amount of nitrogen in a large 

 bulk of rich soil. There is, at least, no evidence to show that 

 either the sand or the garden soil have taken up nitrogen on 

 their own account, independently of the plant. 



In order to show clearly that the gain of nitrogen is far beyond 

 the limits of experimental error, it will be well to give some 

 numerical results showing the actual amounts which had to be 

 dealt with. Leaving out of account the difference in the amount 

 of nitrogen of the seeds sown in each pot —the exact amounts are 

 recorded in the paper — and the slight difference in the initial and 

 final amounts of nitrogen in the sand, the results will be as 

 follows : — In the 9 pounds of sand which each pot contained 

 there was nearly 01 gram of nitrogen. The three seeds sown in 

 each p^t contained nearly 0*03 gram of nitrogen. At the con- 

 clusion of the experiment the vegetable produce contained : 

 pot I, 0*28 ; pot 2, o'54 ; pot 3, 044 gram of nitrogen ; which, 

 after deducting the nitrogen of the seed sown, corresponds with 

 a gain of 0-25, 0*51, and 041 gram of nitrogen. 



The experiments in the second season, 1889, included the 

 following leguminous plants : peas, red clover, vetches, blue 

 lupins, yellow lupins, and lucerne. The sand used this tiniewas 

 a coarse, white sand which was well washed and also sufficiently, 

 if not absolutely, sterilized by heating for some days at nearly 

 Ioo° C. The necessary ash constituents, mixed with an equal 

 weight of calcium carbonate, were added to each pot. There 

 were four pots to each series. No. I contained the prepared 

 sand with nothing further added. Nos. 2 and 3 the same sand 

 to which a soil extract was added— prepared from a good garden 



