of the Organic Systems of Vegetables. 97 



though most abundantly in the shaded ones ; thus shewing 

 the production of carbonic acid in every variety of situation. 

 These experiments were repeated many times. Again, fresh 

 healthy plants were put into bottles as before, but instead of 

 plain water, lime water was introduced ; and after, being in the 

 same situations for upwards of six hours, the lime was found on 

 examination to be precipitated in all. Again, fresh plants were 

 introduced into the bottles with a little plain water as in the 

 first experiment, but closed phials of lime water were likewise 

 put into the larger bottles, which being firmly stopped were 

 put as before in the four different situations, and after six 

 hours, some of them were tested by tapers, which were extin- 

 guished in those in the shade, and burned in those in the light 

 as at first; and then the duplicates of each, by inversion, allowed 

 the lime water to escape from the close phials, and immediately 

 precipitates of carbonate of lime were formed in all. In the 

 foregoing experiments healthy growing plants were invariably 

 selected. In the following, healthy plants were put into some 

 of the bottles, and unhealthy or decaying ones (not dead) into 

 the duplicates : these, as in the previous trials, were placed in 

 the four different situations with regard to light ; at one time 

 the bottles being filled with common air, and subsequently, in 

 repeating the experiments, tapers burned out in each. After 

 six hours they were examined : and first, of those which had 

 healthy plants and which had stood in the sunshine ; tapers 

 when introduced into these burned brightly, both in the bottles 

 which had had them burned out in them before (so that their 

 oxygen had been converted into carbonic acid), as well as in 

 the others ; and thus the carbonic acid must have been recon- 

 verted into oxygen, for that this was the chief source of that 

 gas was evident from the circumstance of the introduction of 

 lime water into some duplicates, when the precipitate was 

 much less than when the carbonic acid was thrown down at 

 first after burning out the tapers, and without exposure to the 

 sun. The air in the bottles which stood in diffuse daylight 

 supported the combustion of a taper when reintroduced, but 

 feebly ; while those in the shade extinguished it at once. The 

 bottles which contained unhealthy plants, with the oxygen of 

 the air converted into carbonic acid by the combustion of a 

 VOL. I. OCT. 1830. H 



