PRODUCTION OF NITROGEN. 183 



809. There are many facts which go to prove that the decomposition of carbonic 

 acid is a secondary result, brought about by the action of nitrogenized ferment in a state 

 of eremacausis, the sunlight operating in the first instance upon the ferment itself. 

 Plants can grow in a certain manner in dark places, and if the observations of botanists 

 have been correctly made, although this kind of growth may be abnormal, it eventuates 

 in increasing the total weight of carbon. It signifies little that in these instances lignin 

 may often be deficient, for other bodies of the starch family make their appearance ; 

 and results of this kind serve to show that, though in all ordinary cases the union of car- 

 bon with the elements of water is an effect of light, there are other cases in which, either 

 by ferment action, or other powers residing in the plant, the same result can be attained. 



810. BOUSSINGAULT states that grass leaves dried in air at 212 Fah., and burned with 

 oxide of copper, yield 1-3 per cent, of their dry weight of nitrogen, which nitrogen is, 

 of course, in combination. I found, however, that there is, besides this, included in the 

 tissue of the leaf a certain quantity of gas, which can be removed by the air-pump. I 

 presume this air is naturally enclosed in the spiral vessels. When leaves are placed in 

 an inverted jar with boiled water in vacuo, this gas is liberated ; at first, most copiously 

 from the fractured extremity; but as the process of exhaustion goes on, it exudes from 

 both faces of the leaf, perhaps by rending open the frail tissue in which it is imprisoned. 

 In leaves that have stomata on one side only, it does not pour forth from those organs 

 in preference to other parts, and from this it may be inferred that it does not normally 

 exist in the intercellular spaces. In a given weight of leaves its amount is very varia- 

 ble, ranging, in my experiments, from -01 to -02 cubic inch for ten grains of grass leaves. 

 Its constitution, as determined by analysis, is also variable, but very remarkable ; it con- 

 tains from 88 to 94 per cent of nitrogen. 



811. It being, therefore, understood that in the tissue of the leaf a certain quantity 

 of gas is mechanically included, which gas differs from atmospheric air in the circum- 

 stance that it contains a larger volume of nitrogen, which may be removed by the air- 

 pump, we are in a condition to understand whether it is this nitrogen which furnishes 

 the supply found in the gas exhaled by leaves. The following experiment proves that 

 it is not: 



812. I removed by continued boiling and exhaustion all the air dissolved in a solu- 

 tion of bicarbonate of soda. I also removed all the nitrogen from some grass leaves, 

 by placing them in vacuo immersed in water that had been boiled and subsequently 

 cooled. Then placing these leaves in the solution of the bicarbonate and in the ves- 

 sels in which the experiment was finally to be conducted, I kept them in vacuo for an 

 hour. This was done to get rid of that film of atmospheric air which always adheres 

 to the surface of glass vessels, and which might have disturbed the result by furnishing 

 nitrogen. The leaves were now exposed in the saline solution to the beams of the 

 sun, and presently the evolution of gas commenced. When a sufficient quantity was 

 collected, it was found to consist of 88 per cent, oxygen and 12 nitrogen. 



813. Repetitions of this experiment prove that, although the nitrogen mechanically 

 enclosed in the leaf to a certain extent mingles with the oxygen evolved, and, indeed, 

 it could not be otherwise on account of the diffusion of gases into one another, yet the 



