THE METABOLISM OF PLANTS. 199 



With regard to the evolution of carbon dioxide, it has been 

 found that it is smaller at low temperatures than the absorp- 

 tion of oxygen, and more considerable at higher temperatures. 



Pedersen determined the amount of CO 2 evolved by Barley-seedlings : 



at 4-5 C. they evolved per hour 9-5 mgr. CO 2 . 



8-1 10*8 



I5-3 16-5 



,, 18*0 24*3 



Similar determinations were made by Rischawi with Wheat- seedlings: 

 at 5 C. they evolved per hour 3-30 mgr. CO 2 . 



15 9-90 



2o 12-54- 



25 17-82 



30 22-04 



,,35 ,, 28-38 



,,40 37-6o 



Dehe'rain and Moissan experimented with leaves : 



TOO grmes. of leaves of Sinapis alba 



evolved in 10 hours 0*240 grme CO 2 at a temp. 14 C. 

 o'72o 31 



0*636 40,, 



, Pinus Pinaster 0*031 o 



0*058 8,, 



v n 0703 3 



I'333 ,, 40,, 



It appears that in the experiment with leaves of Sinapis alba at 

 40 C, the optimum temperature had been surpassed. 



We may further illustrate this point by some of Moissan's results. 



Weight and nature Vol. of O Vol. of CO, Tempe- 



of organ. absorbed in 10 hrs. evolved in 10 hrs. rature. 



10 grmes petals of Yellow Tulip 11*72 c.c. 7-41 c.c. 13 C. 



ii*56 9*95 22,, 



Iris germanica 9-92 7*24 14,, 



,, I3*48 10-34 M 19 



6-53 5-44 ,, 13,, 



loo,, buds of Horse-Chestnut 121*90 99-62 15,, 



59'66 154*00 30,, 



branches 37*33 18-57 15,, 



35*14 87-52,, 30% 



