ON THE RESPIRATORY FUNCTION OF STOMATA. 23 



chamber, it passes to the apparatus where the C0 2 it has 

 taken up is absorbed by the standardised baryta. At 

 the end of the experiment, without interrupting the current, 

 the amount of baryta unneutralised is estimated with the 

 standard acid, and thence the amount of CO, liberated 

 during that experiment easily calculated. 



The area of leaf covered by each capsule is just ten sq. 

 cms., and as the amount of C0 2 given out by surfaces poor 

 in stomata is very small, the experiments on this point are 

 often of twelve hours' duration. 



In the appended table of results the amounts of C0 2 

 evolved, given in the third and fourth columns, are ex- 

 pressed in cub. centims. per hour and ten sq. cms. It is 

 obvious that there is a close general agreement between 

 the distribution of stomata and the exhalation of CO,. 



The very small amount estimated for the upper surfaces 

 of those leaves which are said to have no stomata above, 

 must be partly made up of the C0 2 passing through the 

 occasional isolated stomata which are known to occur in 

 such cases, and partly of the minute amount of CQ 2 which 



