March 29, 1894J 



NA TURE 



511 



Great Eagle Owl {Btibi maxiinns) European, presented by Mr. 

 H. Godman ; two Black Apes {Cynopithectts niger i f, ) from 

 the Celebes, a Greater Sulphur-crested Cockatoo [Cacalua 

 galerita) from Australia, deposited ; two Alpine Accentors 

 ^Accentor collaris) European, purchased ; a Coypu {Myopota- 

 mus coypus) born in the Gardens. 



OUR ASTRONOMICAL COLUMN. 



Photographic Nebulosities in the Milky Way. — 

 In the March number of Astronomy and Astro- Physics, and in 

 several recent numbers of Knozvledge, Prof. E. E. Barnard de- 

 scribes a number of wisps of nebulosity and diffused masses of 

 luminous haze discovered upon photographs taken by him with 

 a portrait lens six inches in aperture and having a focal length of 

 thirty-one inches. A remarkable and large nebulous mass, 

 situated about R. A. 2ih. 34m. Decl. -f 56° 50' appeared upon 

 a plate exposed for seven hours. The picture shows a straggling 

 group of bright stars in the centre of the nebula, which is more 

 than two degrees in diameter. The group of stars is visible to 

 the naked eye as a hazy spot, about three degrees north-west of 

 the variable ^ Cephei, the brightest star in the group being 

 D.M. + 56^26x7. The star D.M. -}- 57° 2309 (mag. 6-5) is also 

 shown by the photograph to be surrounded by a rather un- 

 symmetrical dense circular nebulosity. This object was not 

 previously known to be nebulous, though Prof. Barnard says that 

 with the telescope the nebulosity^can be seen as a hazy glow about 

 the star. The region of the Milky Way lying north and east of 

 Orion appears to be singularly rich in large diffused nebulosities. 

 Photographs show that &> Orionis and A Orionis are nebulous, 

 while there is a faint and large diffused glow near the stars I'and 

 I Orionis. There was a suspicion of a large nebulosity about 

 a Orionis on one of the plates, but this has not yet been verified. 

 The existence of the other nebulosities, however, has been 

 established either by telescopic observation or new photo- 

 graphs. A photograph obtained at the beginning of last 

 month shows two very singular fan-shaped patches of nebulosity 

 close to 7 Cassiopcise. These are about 15' in diameter and 

 point towards the star. They could just be seen by Prof. Bar- 

 nard with the 12-inch of the Lick Observatory, but he thinks 

 they would never have been detected if the photographic plate 

 had not revealed them. Photographs of the region about 15 

 Monoceros show that this group of bright stars is mixed up with 

 misty matter having a diameter of about three degrees. The 

 place of 15 Monoceros for i860 is R.A. 6h. 33m. i6s. Decl. 

 -h 10° I ''3, and the condensation of the remarkable nebula in 

 question is 12' south preceding the star. Prof. Barnard has 

 now photographed the Milky Way from Scorpio to Orion, dis- 

 covering many masses of nebulosity on the way. His pictures 

 are not only beautiful views, but valuable records of the struc- 

 ture of the different regions portrayed. 



Madras Observatory.— From the report of the Madras 

 Observatory, just published in the Monthly Notices of the 

 Royal Astronomical Society (vol liv. No. 4), it appears that 

 the Secretary of State for India has given his sanction to the 

 proposals made by the Government of India regarding the 

 future of the observatory. The observatory, which has hitherto 

 been under the Madras Government, will, from April i, be 

 transferred to the Imperial Government. According to the 

 report, a new observatory for solar physics will be erected at 

 Kodarkanal, on the Palani Hills, under the direction of the 

 present officiating Government Astronomer, who will, for the 

 present, also have charge of the existing observatory. The 

 new institution will undertake the work of solar photography 

 now carried on at Dehra Dun, and will also take up spectro- 

 scopic work on the sun, and actinometric researches. 



A New Comet. — The first comet of this year was discovered 

 by Mr. Denning on Monday evening in R.A. gh. 55m. 

 Decl. -f 32' 15'. It was small and faint, and exhibited a 

 short fan-shaped tail. The object was moving towards the 

 east-south-east at the rate of nearly one degree per day. 



RECENT INVESTIGATIONS AND IDEAS ON 

 THE FIXATION OF NITROGEN BY PLANTS. 

 T^HREE totally different, though convergent, scientific con- 

 troversies have arisen during the latter half of the present 

 century concerning the role played in nature by nitrogen, as 



NO. 1274, VOL. 49] 



met with in the air, rain, and soil, free or combined, in con- 

 nection with the ordinary plants of agriculture and forestry ; 

 and, quite apart from iheir real relations to one another, these 

 three controversies have at times been somewhat confused in 

 their issues. 



One of these controversies turned on the question of the trans- 

 formations of combined nitrogen, as met with in the forms of 

 ammonia, nitrites, and nitrates, and as organic compounds of 

 nitrogen resulting from the decomposition of the remains of 

 living beings — plants and animals— in the soil. The outcome 

 has been the proof that oxidations and de-oxidations of these 

 compounds are intimately bound up with the physiological 

 activities of living organisms, especially bacteria, in the soil ; 

 the investigations of Giltay and Aberson, and Winogradsky's 

 brilliant researches especially, have brought what had long been 

 regarded as purely chemical problems into the domain of biology. 

 "Nitrification" and "de-nitrification," to use the current 

 terms, are phenomena incorporated with those of fermentation, 

 respiration, &c., and therefore involve biological science for 

 their elucidation. 



Another of these controversies turned on the question whether 

 the free nitrogen which forms so large a proportion of that 

 huge gaseous ocean, the atmosphere, can be again directly 

 employed by green leaves, and built up as combined nitrogen in 

 plants; or whether, once having been disengaged from organic 

 and other compounds, and passed into the air as gaseous nitro- 

 gen, it is for ever lost, except in so far as electric discharges and 

 other energetic physical and chemical processes force this 

 relatively inert element into combinations, which the rain then 

 brings down as inorganic salts, and so help to restore the balance 

 of nitrogenous substances in the soil. 



This controversy, a long and involved one, started and for 

 some time continued as a peculiarly chemical question, has 

 passed through various phases and branched out into several 

 subsidiary, controversies, if we may so term them. 



Thus the alleged " fixation" in the soil, especially investi- 

 gated by Berthelot and Andre, became a scientific question 

 apparently on definite lines of its own, and (so far as any such 

 question can be independent) independent of the question 

 whether ordinary green-leafed plants, such as peas, lucerne, 

 wheat, &c. can assimilate the free nitrogen of the atmosphere 

 by processes more or less comparable to those by which they 

 are known to assimilate the carbon they wrench from the 

 carbon-dioxide of that gaseous environment. 



The latter question, again, became a divided one, chiefly owing 

 to assertions that green leaves could directly assimilate the 

 ammonia, if not the free nitrogen, of the aii", and some time was 

 occupied in arriving at the conclusion that ordinary green plants 

 do not directly assimilate or fix either the gaseous ammonia or 

 the free nitrogen of the atmosphere. This conclusion, in 

 opposition to that arrived at by Ville, was regarded as so 

 thoroughly established by the experiments of Boussingault and 

 of Lawes, Gilbert, and Pagh, that it has been definitely 

 accepted and taught for many years — and rightly so, from the 

 evidence to hand. 



The third of the three controversies referred to at the outset, 

 is the more recent one concerned with the question whether 

 certain of the higher green-leafed plants, particularly those 

 known as leguminous plants (such as peas, beans, clovers, 

 vetches, lupins, robinia, &c.), when living as they normally do 

 in symbiotic association with certain microscopic and essentially 

 parasitic fungoid organisms which invade their roots, are 

 differently placed from other green plants as regards the power 

 of " fixing," and assimilating, the free nitrogen of the 

 atmosphere. 



The present position of opinions on this last and most remark- 

 able controversy is the subject of this article, so far as it can be 

 done justice to in the short space at disposal. 



It is now well known that leguminous plants are normally found 

 to have certain nodosities or swellings on their roots, and that 

 these swellings are caused by the activity of certain minute 

 organisms which, as the writer of this article first proved, in- 

 vade the roots from outside, after the manner of a parasitic 

 fungus. The controversy as to the exact nature of these organ- 

 isms — ^bacteria, according to Prazmowski, Beyerinck, and 

 others, degraded allies of the Ustilaginese, or some lower fungus, 

 according to my observations, and the confirmatory evidence of 

 Laurent — in no way affects the truth that these organisms do 

 not kill the plants attacked, or even make them diseased, but 

 incite them to more active life for a time. The evidence on 



