165 



(lomnndinj? solution. Tho partioulnr hyi)othesis rosardiiifj the oauso of clover 

 faiiiin' wliicli I have offered is ji hypothesis only, sot up to he estai)lished or 

 overtlu'own liy futun- invest iiration. and set up in the hope that souiewliere 

 the investigator may he found who can iniravei tlie tangle wliicii tliis particular 

 prohleni presents, and that somehow the means for acconiplishini,' tins jrreat 

 task may he placed at his disposal. 



Jacob (i. LiP.\t.\N. of New Jersey. We should differentiate, it seems to me. 

 in the study of soil acidity and its relation to crop production, hetween the 

 Iturely physiolouici! inllucnce that soil acidity may liavt^ — namely, the iurtuence 

 of the dialysis, or the diffusion of the salts, orpuiic and inorganic, outward and 

 inward, taking the plant roots as the dialyzinj; memhrane — and the hacterioloj;- 

 ical effect. 



Take the case of tiie success or failure of clover. Why is it that clover does 

 not grow well in acid soils? Is it hecause there are certain orfianisms in the 

 soil that interfen> with proper f^ermination or that exert a solvent action on the 

 young roots, and thus destroy or inidermine the vit.ility of the younii plant : is 

 it hecause ther*' are certain ;ici<l stihstances produced in tiie soil which intci'fere 

 with ])r()iter dialysis: or is it bec:\nsc those substances interfere with tlie bac- 

 teriological cooperation that is necessary in order that a clover crojt — a succe.ss- 

 ful clover crop — might he produced? Of course we do not know just what the 

 mechanism of nitrogen H.xation is in the clover i)l;int. We assume — at least 

 those of tis who have given more or less attention to the subject — that the first 

 product ill tile synthesis of inMteiii iiodies is ;i soluble organic nitrogenotis 

 substance, and, being soluble, it is liable to diffust- outward through the root or 

 through the tubercle proper, and there is no doubt that this substance, diffused 

 outward, influences materially the character of the bacterial growth outside ')f 

 the root tubercles, lliltner. of (Jermany. has proposed a theory according to 

 which it is not sutticient to have the proper bacteria ; that is, I'xviKloiiionas 

 ■Kuliricdiii alone is not usually sutlicient for the growth of leguminous i)lants. 

 lie claims that within the sphere of root action, in the innnediate vicinity of 

 the roots and tultercles. there is a bacterial flora which plays an important i)art 

 in the normal developnjent of the clover; and he thinks he has proved, with 

 regard to these bacteria, that the first service that they render to the legumi- 

 nous crops is by consuming the store of nitrates iu the soil. He says that, since 

 it is proved that the fixation of nitrogen by leguminous crops is discouraged by 

 the presence of nitrates, it follows that this withdrawing of the nitrates fnmi 

 the legiuninous crops encourages the fixation of nitrogen. 



Whether that is true or not remains to be demonstrated. But there is 

 another point of view, and that is that the soils which are acid, the flora, the 

 bacterial flora, is entirely different from that in alkaline soils, and we know that 

 in certain changes in the soil the formation of soluble nitrogenous substances may 

 keep pace with the formation of the insoluble nitrogenous substances. We may 

 take, iu the laboratory, a ctilture solution containing sohible nitrogenous substances 

 and convert the latter, by inoculation with certain bacteria, into insoluble 

 modifications without the loss of any nitrogen whatsoever. Similarly, the soil 

 nitrates on the soluble organic compounds may be rendered insoluble as fast as 

 they are formed. 



If, in the presence of soil acidity, the flora will prevail which will cause the 

 transformation of the soluble into insoluble nitrogenotis compotuids, tlien condi- 

 tions are thereby created that have a very important bearing on crop production. 



And, furthermore, if we assume that there are soluble nitrogenous compounds 

 formed within the root tubercles of leguminous plants that they diffuse outward, 

 and that they are rendered insolulile as they leave the plant, then it follows 

 that the dialysis will he thus accelerated, and the nitrogenous substances will 



