72 THE POPULAR SCIENCE MONTHLY. 



of them, contain always more or less green matter, masked. They also 

 possess the property, which the white leaves do not, of absorbing car- 

 bonic acid, and exhaling oxygen in a perceptible degree, when exposed 

 to the sun. We lay stress on these phenomena, since it is for want of 

 having understood them that very recent authors describe colored 

 leaves as being usually deprived of the function of assimilation. 



If we make the experiment already desci'ibed with white leaves, 

 we shall find that in the daytime they exhale a perceptible amount of 

 carbonic acid. 



Sennebier had observed that the yellow and red stripes of the Ama- 

 rantus tricolor do not give off oxygen when exposed to the sun, but 

 that the leaves of the Amarantus ruber, on the contrary, possess this 

 property. So, too, leaves naturally green, which change color at the 

 close of their life, entirely cease from absorbing carbonic acid and ex- 

 haling oxygen. Corenwinder has shown that faded leaves that are on 

 the point of falling constantly give out carbonic acid. The fact seems 

 to be universal. Here, however, it is not a phenomenon of vitality 

 that appears, but an act of decrepitude, which goes on and increases 

 after the leaf has fallen. 



We observe the same jmenomena in other plants, some of whose 

 leaves contain no green matter whatever, especially in the striped ma- 

 ple, which is such an ornament of our gardens in summer. In August, 

 1868, M. Corenwinder gathered off one and the same maple some 

 leaves that were perfectly white, and others that were perfectly green, 

 and analyzed them to determine the amount of nitrogen they respec- 

 tively contained, with the following results : 



WHITE LEAVES. 



Nitrogenized matters in 100 grammes, dried at 212 Fahr 17.06 gr. 



GREEN LEAVES. 

 Nitrogenized matters in 100 grammes, dried at 212 Fahr 13.75 gr. 



Thus we find a much larger amount of nitrogenous elements in the 

 white leaves than in those which contain chlorophyll ; on the other 

 hand, the latter are richer in carbonaceous substances. These two 

 observations clearly confirm M. Corenwinder's theory. 



Finally, we may conclude, from all the analyses and experiments 

 we have here detailed, that there exist in plants, at every stage of 

 their life, two distinct functions having different centres of action. 

 The one is respiration, which depends upon the nitrogenous organic 

 bodies. The other is assimilation of carbon, which has its seat in 

 special organisms, formed principally, if not exclusively, of ternary 

 elements. 



This theory gives a natural explanation of all observations upon 

 the physiology of leaves. M. Corenwinder hopes soon to make an 

 application of it, and will show what it is worth, by explaining, with 

 its aid, the origin of carbon in plants. 



