273 Notices respecting Kew Boohs. 



acquire an acldilionril weight in proportion ; which is con* 

 trarv to the fact proved by direct experiment. Peas im- 

 mersed in water bv Cruickshank gave out carbon when no 

 germination took place, and when they approached the pu- 

 trefactive process, in which case the quantity of air was in- 

 creased. But where germination took place, and oxygen dis- 

 appeared and carbon appeared, the quantity of air was not 

 increased but rather diminished. Hence it is inferred, that 

 the oxvgcn which disappears is not all absorbed by the seed 

 in germinating, but only such a quantity as is merely equi- 

 valent to counterbalance the loss of carbon which unites 

 with the oxygen to form carbonic acid, and in this manner 

 effects a change in the volume only, and not in the weight 

 either of the germinating seed or the incumbent gas. Mr- 

 Ellis concludes, that " in germination the seed does not 

 form carbonic acid from its oivn substance, but furnishes 

 only one of the constituent parts of it, namely, the carbon ; 

 ■ and that when it does form this acid, independent of oxygen 

 gas, it is only under a state of decomposition, or in circum- 

 stances where no living action is going on." It is also ob- 

 served, that the quantity of carbonic acid produced does ac- 

 tually exceed in weioht the oxygen that disappears; and that 

 as " carbonic acid is necessarily a product and consequence 

 of germination, it seems absurd to consider it at the same 

 time as an existing principle and a cause." Heat, moisture, 

 and oxygen, he has proved essential to the process of ger- 

 mination : but liow these substances act on each other so 

 as to produce carbonic acid he has not ventured to deter- 

 mine, as the disenjiaerement of a new substance in this case 

 cannot be accounted for as it can be in that of combustion. It 

 may be alleged, however, that the water gives mechanical ex- 

 pansibility to the seed, that the heat then cflccts its expansion, 

 and that in the latter process the carbon is brought to a state 

 fit to conibine with the oxv^en, and thus form carbonic 

 acid. 



In the second chapter Mr. Ellis examines the changes in- 

 duced on air by vegetation, in which he combats the opi- 

 nion respecting the alternate emission of oxygen and nitro- 

 gen gases by plants^ and observes, that *' both physiologist? 



and 



