ASPECTS OF AN OLD AGRICULTURAL QUESTION. 255 



The study of the insectivorous plants, especially by 

 Darwin (7), showed clearly that, in some cases, at any rate, 

 there exists arrangements for acquiring nitrogen very 

 directly from animal bodies. 



All these examples of what may be called small circula- 

 tions of nitrogen do not really affect the question of the 

 great circulation of this element in Nature, and much 

 concern was expressed by those who asked : Whence come 

 the new supplies of nitrogen to replace the enormous loss 

 which is continuously going on as the nitrates drain into the 

 subsoil, beyond the reach of the roots, and into the rivers, 

 and eventually to the sea ? One of the two things must be 

 happening ; either the surface of the land is becoming 

 slowly deprived of the nitrogen supplies alone available to 

 plants, or the vast extents of untouched prairie-land, forests, 

 etc., in various parts of the world, are kept in balance by the 

 continuous supplies of atmospheric nitrogen compounds due 

 to electric discharge sufficing to cover the loss always going 

 on below. 



Many people were not satisfied that this supply of sub- 

 aerial nitrogen compounds was sufficient to cover the loss, 

 even allowing that the slow disintegration of rocks below, 

 and the bringing to the surface of the nitrogen containing 

 minerals by capillarity, action of worms, and other agencies, 

 delayed the final but inevitable loss. Besides, .old meadows 

 annually cropped, but not manured, were found to give 

 steady crops. But another set of ideas had begun to 

 influence the matter, starting from what was at first an old 

 point of view, and developing into a doctrine which has 

 done more to revolutionise agricultural science than any- 

 thing since the explanation of assimilation. 



The older observers would have had great difficulty in 

 conceiving of the soil in which plants grow as anything 

 more complex than a mixture of sand, clay, lime, and bits of 

 other dead substances, but a modern botanist realises that it 

 is a far more delicate and intricate medium than that. 



The neighbourhood of the finest rootlets of a bean, 



•lucerne, wheat plant, oak, or pine, offers to us a field of 



research, which only stops short of bewildering our ideas 



