148 THE ROTHAMSTED EXPERIMENTS. 



Fig. 5 ex- results. As with the other plants, sterilised sand with ash 

 plaimd. were uge(i in potg j 2> an( i 3^ Dut pot 4 was filled with sandy 



soil from a field where lupins were growing. Pot 1 was left 

 without microbe-seeding, but pots 2 and 3 were microbe- 

 seeded by a watery extract of the lupin-soil instead of garden- 

 soil as in the other cases. The results with the yellow lupins 

 were as follows : In the sterilised quartz sand, without mi- 

 crobe-seeding, the growth was extremely limited, both above 

 and under ground. Under the influence of the lupin-soil 

 extract seeding, the above-ground growth was not only very 

 luxuriant, but the plants developed considerable maturing 

 tendency, flowering and seeding freely. The development of 

 the roots generally, and that of swellings or nodules on them, 

 were also very marked. In pot 4, with the lupin-sand itself, 

 which would supply a not immaterial amount of combined 

 nitrogen, although the growth was fairly normal, it was, both 

 above ground and within the soil, much less than in the pots 

 with sand and the soil-extract only ; and the development of 

 nodules was also less. It was concluded that the less growth 

 in the lupin-sand itself than in the quartz sand with the lupin- 

 soil extract was largely due to the much less porosity of the 

 lupin-soil, especially when watered. 



Again, as with the peas and vetches, so with the lupins, 

 without microbe-seeding there was very limited growth, no 

 formation of nodules, and no gain of nitrogen ; but with 

 microbe-seeding there was luxuriant growth, abundant nodule- 

 formation, and, coincidently, great gain of nitrogen. There 

 was, in fact, very many times as much nitrogen in the 

 products of growth as in the seed sown. See fig. 5. 



In the experiments with the fourth annual, the beans, 

 the plants suffered much from aphis ; the growth was con- 

 sequently very limited, and the gain of nitrogen but small. 

 Results The results with peas, vetches, and yellow lupins are, how- 



definiteand ever) vei y definite and very striking. They are abundantly 

 illustrative of the fact that, under the influence of suitable 

 microbe-seeding of the soil, there is nodule-formation on the 

 roots, and, coincidently, increased growth, and gain of nitrogen 

 beyond that supplied in the soil and in the seed as combined 

 nitrogen ; presumably due to the fixatiou, in some way, of free 

 nitrogen. 1 



As already said, experiments were also made with four 

 plants of longer life — white clover, red clover, sainfoin, and 

 lucerne. 



1 M.M. Schloesing^s and Laurent have shown, by growing Leguminosse 

 in closed vessels, and by the analysis of the air before and after growth, that 

 free nitrogen disappeared, in quantity closely corresponding to that gained in 

 growth ; thus establishing the fact that the source of the gain was free 

 nitrogen (Compt. Rend. cxi. 750). 



