370 THE CHEMISTRY OF CREATION. 



the day long, in return for the carbonic acid 

 it absorbs. It also begins rapidly to form 

 wood ; and we shall soon find that all the parts 

 of the plant have acquired the hardness and 

 firmness peculiar to woody tissues. The next 

 important period in the history of the plant is 

 its flowering season. The flowers, instead of 

 decomposing carbonic acid, on the contrary, 

 give out that gas, and absorb a considerable 

 quantity of oxygen from the air. At the time 

 of ripening, the fruit also absorbs oxygen 

 from, and gives carbonic acid to, the air. In 

 addition it is stated, that all the parts of a 

 plant not having a green colour, such as the 

 bark, absorb oxygen and eliminate carbonic 

 acid gas. 



These effects the alternate decomposition of 

 carbonic acid, and evolution of oxygen, with 

 the contrary process of absorption of oxygen, 

 and evolution of carbonic acid, appear to be 

 all dependent entirely upon the alternate pre- 

 sence or absence of the solar beams. The plant 

 is influenced in succession by the chemical rays, 

 by the luminous, and by the calorific or heat- 

 rays. The luminous or pure light-rays cause 

 its leaves to decompose carbonic acid ; and 

 under their influence alone is the green colour, 

 which is due to a substance named chloro- 

 phylle, produced. By the light-rays, therefore, 



