OF CARBON. 49 



of nourishment. The power of absorbing nu- 

 triment therefore from the atmosphere, with 

 which the leaves of plants are endowed, being 

 proportionate to the extent of this surface, 

 every increase in the size and number of those 

 parts is necessarily attended with an increase 

 of power, and, in consequence, to a certain ex- 

 tent, farther development of new leaves and 

 branches. 



This process is continually in operation ; it 

 comaiences with the first formation of the leaf 

 and does not cease with its perfect development; 

 but the matters derived from the continued 

 assimilation by the perfect leaves are no longer 

 employed in their own increase, they now 

 serve for the formation of woody fibre, sugar, 

 starch, &c. in the ripening of the fruit, when 

 the functions of the leaves of most plants 

 cease, because the products of their action are 

 no longer required, and they then yield to the 

 action of the atmosphere, change their colour 

 and fall off, or, as in annuals, they partake of 

 the general decay of the whole plant. 



A vast deal of controversy has taken place, 

 on the subject of the absorption of carbonic 

 acid gas by plants, by authors of considerable 

 ability on both sides; but the details here intro- 

 duced, are, it is imagined, sufficient to prove, 

 both by direct and collateral arguments, that 

 the view now taken is correct, and it is gene- 

 rally admitted to be so by the most eminent 

 physiologists of the present day. It will be 

 desirable however to continue the subject far- 

 ther, and detail some of the experiments made 



