DURING THE GROWTH OF PLANTS. 405 



of the atmosphere. They were accurately weighed in this condition, a portion of each 

 part, or of the entire mass, subjected to ultimate analysis, and calculation made for 

 the whole. Thus I was enabled to discover an increase or decrease of any of the 

 elements in any experiment so conducted, wherein the seed itself, the water, and the 

 atmosphere furnished whatever was required for vegetation. The experiments which 

 have reference to this part of the subject are found in Table X. 



We are led by these experiments to the inference, that, independent of that indefi- 

 nite quantity of nitrogen which is given off to the atmosphere during vegetation, there 

 is an increase of this element in plants when compared with its quantity in the seeds; 

 and in this case the seeds form the only source from whence they could derive it, 

 with the exception of the atmosphere and any little which might have combined with 

 the water used on the occasion. 



It would be at variance with my mode of research, which is purely experimental, to 

 make any observations upon the quantity of nitrogen which is probably furnished by 

 the atmosphere during the germination of seeds and the full growth and develope- 

 ment of plants. The experiments before us dispose us to infer that it differs with the 

 temperature at which the plants are exposed, and with exposure as regards sunshine 

 and the shade. Thus we have in the germination and vegetation of barley, for in- 

 stance, the quantity of nitrogen in the grain germinated under very favourable cir- 

 cumstances for the process, increasing to an extent equal to thirty- eight per cent, 

 upon the original quantity contained in the seed : when the same kind of barley was 

 kept under unfavourable circumstances for vegetation, and allowed to grow until the 

 principal part of the farina was exhausted, the increase in the quantity of nitrogen 

 was only eighteen per cent. When the same grain was allowed to vegetate in the 

 sun*s rays until about two-thirds of the flour contained in the seed had disappeared, 

 the increase in the quantity of nitrogen was thirty per cent. ; and when the same 

 plants were kept under the most favourable circumstances, and allowed to vegetate 

 until the seeds appeared to be exhausted, the young plant during this time having 

 the most healthy appearance, there was an increase upon the quantity of nitrogen 

 contained in the seeds of nearly Jifty per cent. 



Seeds of cress during vegetation increased their quantity of nitrogen forty-one per 

 cent, when the plants were kept under a temperature varying with shade and sun- 

 shine from 60° to 84°. The experiments upon the seeds of the turnip, an important 

 plant in an agricultural point of view, (about one half of which germinated,) shows 

 that the nitrogen which was derived from the atmosphere was more than that which 

 was contained in the seed. In all these experiments we have the quickness of the 

 growth of the young plants proportional to the quantity of nitrogen present when 

 compared with 1000 parts of carbon in the same. 



With these facts before us, we are enabled to account for plants not continuing to 

 grow so well in pure oxygen gas as in atmospheric air ; and by following up. the in- 

 quiry in other departments, we see the wisdom of the all-wise Contriver in consti- 



