THE SOURCES OF THE NITROGEN OF VEGETATION, ETC. 527 



A reference to Table XII. will show the numerical results of this experiment with 

 beans in 1857. 



The beans and peas of 1858, the particulars of which are also given in Table XII., 

 did not grow so satisfactorily as the beans of 1857, last noticed. Yet the beans of 

 1858 gave more than three times as much organic matter in the produce as was con- 

 tained in the seed, and they appropriated even a much larger proportion of the Nitrogen 

 of the seed than did those of 1857. The result with the peas was not so satisfactory, 

 owing to the less healthy character and the more limited amount of their growth. 



From the fact that these Leguminous plants did not go through a complete course of 

 growth to the flowering process, it may be objected that hence they did not pass certain 

 stages of growth in which they might possibly assimilate free Nitrogen. We shall refer 

 to tliis objection again further on. At present we confine attention to the important 

 fact, that active growth has taken place — that the process of cell-formation, with the 

 accompanying one of the decomposition of carbonic acid and the fixation of carbon, has 

 gone forward with a deficient supply of combined. Nitrogen, and in the immediate pre- 

 sence of free Nitrogen, and yet none of it has been assimilated. The plants have in fact 

 been subjected to a considerable range of the conditions which were considered, ajjriori, 

 to be favourable to the assimilation of free Nitrogen ; and yet this has not taken place. 



It is a fact observed in agriculture, that manures rich in organic matter frequently 

 favour the growth of Leguminous crops. We shall not here discuss the question 

 whether these organic manures, as such, act simply as a source of carbonic acid, or of 

 carbon compounds of a more complicated character. We would, however, call attention 

 to the fact that, in the case of the experiments now under consideration, the vital forces 

 were sufficiently energetic to perforin the function of cell-development and multiplica- 

 tion, from carbonic acid as its source of carbon ; yet these forces, capable of effecting 

 this result, have been incapable of effecting the appropriation of free Nitrogen. 



Buckwheat. 



The evidence afforded by the numerical results in the Table XII. relating to this 

 plant is not of so decisive a character as that with regard to the cereals, or even to the 

 Leguminous plants ; for the quantity of dry matter in the produced plants is less than 

 that in the seed sown, whilst the Nitrogen in the plants is little more than one-third 

 that of the seed. But when we come to compare the results of the experiments with 

 Buckwheat grown with and without the supply of ammonia, it will be found that the 

 physiological evidence of the dependence of vegetable growth upon a constant supply of 

 combined Nitrogen is stronger in the case of these plants than in that of the cereals. 

 The small proportion of the total Nitrogen of the seeds which the buckwheat seemed 

 capable of appropriating might lead to the inference that, ceasing to grow with an 

 abundance of combined Nitrogen apparently at its disposal, it had done so for some 

 other reason than the want of available Nitrogen. But this question was set at rest by 

 the fact that, on the addition of an amount of ammonia very small in its contents of 



mdccclxi. 4 c 



