72 



iKisii (;.\Ki)i:NL\(i 

 The Food of Plants. 



r.> Ciii^.Mi-r. 



TliK valiif ..1" i-i-as. h.aiis ami lu|.iii> as \ riirt alilf 

 rn,.(l Nsas ivrn-iiisfd l.-n^' lu-f.-iv (!.,• lira.- »i 

 Li.-l.iK ami (lu- julvrut ..f analytical .li.-iiiislry. 

 Tlu- chfinisl fxplains ii«.\v lliis hi^'ji f.n.d valiu- 

 is iliu- («> tln'ir richm'ss in jirotfids. tin- iiilin^'i'm'iis 

 niatrrial fiuiii which (he nervous and iuns( iilai 

 tissues of ..nr lu.dics liave l.ccn IniiK uj. and 

 from wldcli the wast.a^'e <d these tissues due 

 (u the wear and tear of life is niatle ^ood from 

 day to day. Now. it nu^dd natujally he inferred 

 Ihat tliese i>i'as. heans antl luiiins. owiiiK 1" 

 llieir ricliiu'ss in iulroj,'en. should, when raised 

 as cro|is. he s|)iTially seveie on the laud, and 

 reiiuire an extra allowance <d iutro^euo\is manure. 

 l'-xi>erience. however. show«-d that this was not 

 tlu- case. The.st' lefiuuu-s. it was known, were 

 not by any nu'un.s .severe or exhausting crops. 

 On the contrary. Yet tlie nitrogen nuist come 

 from sonu'wliere. Hen<-e the need becauu' 

 ai.i>ari-nt for a seientitic /Uld experinu'ut hearing 

 on the question, and. accordinglv. an experinu'nl 

 of the kind was carried out at Altmark in 

 (lermanv. tin- results of which were luihlished 

 in 1881." 



A piece of groimd of i-ather poor ((ualily. which 

 had, not been tilled, or manured, foi' a lUMuher of 

 > cars ]ireviously. was crojtped with lu])ins for 

 tifteen years in successioi\. Dressings of Jiunerals 

 were given annually, but no rdtrogen com- 

 ]iounds whatever. When the cro]) readied 

 maturity it was cut and removed, every year in 

 due course. At tlie beginning of the experinu^nt 

 the services of a chemist were requisitioned to 

 make an analysis of the soil and subsoil, with 

 regard to the amount of combined nitrogen 

 present ; and a sindlar analysis was made, 

 at the end <»f the experinu'ut. fifteen years later. 

 Tlie results of the analyses may be seen at a glance- 



It will be observed tliat despite the heavy 

 annual drain of nitrogen, due to the removal of 

 the cro]), without any eomjiensating return of 

 nitrogenous manures, yet both the soil and 

 sub.soil actually grew richer in nitrogen. This 

 ex])eriment proved beyond a shadow' of dou))t 

 that atmospheric nitrogen was " lixed " in some 

 Avay by the lui)in cro)!. It was not equally clear, 

 however, that this unique power was ])os- 

 «essed by plaids in geiu-ral. Certain plants 

 seemed to be favoured — lu])in. i)eas, beans, atul. 

 of course, <-Iover — all belonging to one fandly 

 t^Hj. 13ut why was it they lost the ])ower when 

 grown under the conditions of Boussingault's 

 experiment? The question was more easily 

 asked than answered, and needless to say gave 

 rise to much discussion. Indeed, the whole 

 subject of nitrogen assimilation seemed to be 

 once more in the melting pot. But at any rate 



it ua> rl.ar I lirie must he soiue unknown factor 

 op, latin- ill the soil under natural .onditions 

 uhi.h was altogether missing in the artili<ial .soil 

 made up of sand an<l wood ashes. 



Some clue as to tin- natun- of this uiiknoun 

 factor was suppli.-<l hv the res.'aich.s of I'.isteur. 

 carrie<l. on aliout the >..mc time in quit<- another 

 field of impiirx. In stinlving feinient at ion, 

 i'asteiir was led to the c.mc'liision that certain 

 . hrmical chang.s were brought about by t he 

 .111 ion of mici'o-organisms. .Vhoholic fermenla- 

 tion. for instaiKe. was due to the veasf organism. 

 Other oig.iiii',ms prod,u<'e<i putrefaction and 

 (h'cav. and. siiiiiiailv with I'egarcl t<» <lisease. In 

 a word, r.isteur hv'his res. -arches w;is lavinu lli.- 

 foututatioiis of tin- ii.-w s.i.ii.r ,,\' bact .-riology . 

 As som.' uiitiT expi'i-ssc.l, it in an. d her wav. 

 Past. -in- l.v his ivsear.h.-s has s.-t up for us th.- 

 .■iu|.ir.- of the nii.r.d... in additi.m to the ..th.-r 

 pow.'is we ha\c to sti'uggle against. Hut in 

 passing it may b.- pointed out that lie al.s.. 

 I.'d the way in showing how (he ]>.>wer .d this 

 n.-w .-midre ndght be i-esist.-d. ami even turiu-d 

 to go.id account. In this way his researchi-s 

 have benelit.-d Kranic to an extent sullicient 

 (in Huxley's opinion) to make up for the war 

 indemnity of 187(1. Science, n.)t so much f.>r 

 its .)wn sake as for the sake <d hunuinity an. I 

 the welfare of his own beloved, France, seenu-.l 

 ind.eed to be the i<i.'al of the great Krenihman. 



it was easy to imagine that these seemingK 

 ubicpiitous micro-. )i-ganisms of I'asleur might Im- 

 Itresent in the s.iil. busy at w.)rk. bringing about 

 chemical changes in a manner imt hith.-it.. 

 realised.. One such chemical change, the con- 

 version of anuuonium com])ounds into nitrates 

 (nitrifi.ati.,n). was sli.iwn (1877) bv Warington. 

 ..f Kothampst.-a.l,, to be du.- t., bacterial agency. 

 The .hange was l)rought ab.mt in two stages by 

 two (Uflcrent s|)ecies of .u-ganism. one species 

 taking up the work wliei-e the .)ther left off. It 

 was just i).)ssible that the mysterious fixation of 

 atniosplierii; nitrogen by lu])ins and other legu- 

 minous plants might be due to the same cause. 



The matter was investigated by two (lerman 

 scientists — Hellriegel and Wilfart— in a classical 

 research, the result of which was ])ublished in 

 1888. They worked with })olh lujiins and p<'as. 

 whi.-h they grew in sterilis.-d, sand,, the n.-cessary 

 nun.-ral f.xxl being added th.-i-.-lo, but no nitrogen 

 com]i.)und whatevei-. BoussingauH "s pr.-vi.ius 

 results were conlirmed- The ])lants grew all right 

 for a little while, and then a'l growth was arrested. 

 Next, some soil extract was ad.dcd. and wher.'vei- 

 this treatnrent was followed the ])lants grew and 

 flourished. It made all the difi'erence between 

 growth and no growth. The difference was not 

 due to any food value in the soil extract itself, 

 because when this was heated t<i 70° C there was 

 no result, the extract had lost its powder. The 

 ])ower evidently was due to some form of life in 

 the extract, to the a(-tivity of some nu<-ro- 

 organism whose oi-d,iuai-v habitat was lb.- soil. 

 Further, it was found IIimI this .soil <-xt la.l . s.. 

 efT.-ctive with lupins and. jieas. had n.> elT.-.t w h.-ii 

 appli.-d, in the case of plants not bel.mging t-. 1 h.- 

 l.-guminous familv. 



Another matter that attra,ct.>d a,tteiiti..n was 

 the ])resence of root nodules in the lu]dns and 

 ]>eas whenever these were grown under the soil 

 extract treatment : whereas when grown by the 

 aid of nitrates in sterilised sand or water cultures 

 the nodules were absent. They nmst be due 

 therefore to the activity of the organisms or 

 bacteria, to use the more common term. That the 



