aud of Carbonates by the Light of the Sun. 171 



Liebig has shown that ammonia exists in the ascending sap. 

 It is probable, therefore, that it does not undergo final change 

 before reaching the upper face (sky-face) of the leaf. There, 

 if it be in the form of a carbonate, it unquestionably is con- 

 cerned in decomposition. With the natural experiment be- 

 fore us, we might expect that the carbonate of ammonia used 

 in place of the soda salts of the last experiment would yield 

 like them. Accordingly it will be found, by using the officinal 

 sesqui-carbonate of ammonia, that leaves effect its decompo- 

 sition. In numerous experiments it has yielded me gas fre- 

 quently containing more than 90 per cent, of oxygen. 



In every instance which I have examined the gas evolved 

 from leaves is not pure oxygen, but, as has been said, a variable 

 mixture of oxygen and nitrogen. This result is of uniform 

 occurrence ; I have observed it in low latitudes where the sun 

 is extremely brilliant, in the case of different plants; and on 

 referring to Dr. Daubeny's paper, it will appear that he has 

 uniformly recognized the same result in England. The very 

 remarkable qualities which certain nitrogenized substances are 

 known to exhibit, acting as ferments as they are undergoing 

 decay, might lead to the suspicion that the decomposition of 

 carbonic acid by leaves is due to the action of some nitro- 

 genized body, the eremacausis of which is promoted by the 

 rays of the sun. 



There are many facts which go to prove that the decomposi- 

 tion of carbonic acid is a secondary result brought about by 

 the action of a 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 carbon 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. 



Boussingault states that grass leaves dried in air at 212° 

 Fahr., and burnt 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, in- 

 cluded in the tissue of the leaf, a certain quantity of gas which 

 may be removed by the air-pump. I presume this air is na- 

 turally inclosed in the spiral vessels. When leaves are placed 

 in an inverted jar with boiled water in vacuo, this gas is li- 



