144 



THE ROTHAMSTED EXPERIMENTS. 



Negative 

 results. 



Berthelot'. 

 views. 



Recent 

 Rotham- 

 sted trials. 



Root-nod- 

 ules and 

 gain of 

 nitrogen. 



Such, then, were the negative results obtained when plants 

 were grown under conditions of sterilisation and of enclosure. 

 There vjos, under such conditions, no gain from free nitrogen, 

 in the growth of either Graminece, Leguminosos, or other plants. 



Recent Experiments, which do show Fixation of Free Nitrogen. 



It was about the year 1876, that M. Berthelot called in 

 question the legitimacy of the conclusion that plants do not 

 assimilate the free nitrogen of the air when drawn from the 

 results of experiments in which the plants are so enclosed as 

 to exclude the possibility of electrical action ; and later he 

 objected to experiments so conducted with sterilised mate- 

 rials, on the ground that, under such conditions, the presence, 

 development, and action, of micro-organisms are excluded. 

 So far, however, there is nothing in the recent results, either 

 of M. Berthelot himself or of others, which can be held to 

 invalidate the conclusion which had been drawn from the 

 results of Boussingault, and from those obtained at Eotham- 

 sted — that the higher chlorophyllous plants do not directly 

 assimilate free nitrogen. 



Let us now consider what are the results obtained when 

 the conditions of growth involve neither sterilisation nor 

 enclosure. 



A preliminary series of experiments was commenced in 

 1888, and a more systematic one in 1889. The plants were 

 grown in specially made pots, and arranged in a glass-house. 



In 1888 peas, blue lupins, and yellow lupins, were grown, 

 and there were four pots of each : 1. with washed sand, and 

 the ash of the plant added, but no supply of combined nitro- 

 gen beyond a small determined amount in the washed sand, 

 and that in the seed sown ; 2. with similarly prepared sand 

 (and ash), but microbe-seeded with the turbid watery extract 

 from a rich garden-soil ; 3. duplicate of No. 2 ; 4. with the 

 rich garden-soil itself. There was, under the influence of 

 soil-extract microbe seeding, considerable formation of nodules 

 on the roots, and considerable gain of nitrogen. 



In 1889, as already said, a more extended series was com- 

 menced. It included experiments with four annuals — namely, 

 peas, beans, vetches, and yellow lupins ; also with four plants 

 of longer life — white clover, red clover, sainfoin, and lucerne. 

 And, as will be seen further on, experiments were commenced 

 in 1890 with the same four annuals, and the same four plants 

 of longer life, on somewhat different lines from those above 

 referred to. 



Eeferring to the experiments in the glass-house, it may be 

 stated that in 1889 and subsequently a purer white sand was 



