150 



Mr. F. Kidd. 



age, water- content, stomatal aperture, and the consequent uncertainty in 

 obtaining parallel lots such as are required for this method. Owing to these 

 difficulties the results obtained were not so regular as in the case of seeds. 

 It appeared, however, that when " starch " leaves were used a retardation 

 under the influence of CO2 occurred for a short period, but passed away as 

 time went on. The leaves were, of course, kept in the dark during these 

 experiments. The passing of the C0 2 retardation would correspond with the 

 onset of starvation. When starved leaves were used, on the other hand, the 

 same retardation was not observed. Both anaerobic and normal respiration 

 were tested. In order to obtain the effect of C0 2 concentrations upon 

 floating respiration alone equal lots of starved and starch leaves were set up 

 under equal conditions for the desired concentration of CO2. The difference 

 between the respiration of the " starch " leaves and the starved leaves was 

 taken as the value of the " floating " respiration. This subtraction method 

 of determining the floating respiration is used tentatively. It gives, however, 

 a definite result with regard to the effect of CO2 upon floating respiration in 

 agreement with our hypothesis. The fact must be borne in mind that this 

 subtraction method depends on the assumption that the nature and amount 

 of the protoplasmic respiration are the same in conditions of starvation and in 

 conditions of full supply. Further results are awaited here. 



Table IX. — Showing the Retarding Effect of Carbon Dioxide upon the 

 Anaerobic C0 2 Production of " Starch " Leaves (Cherry Laurel), disap- 

 pearing as starvation sets in and completely absent on the fifth day. 





Anaerobic CO- 2 production in successive periods. 



Initial C0 2 in No. 











1st day 



2nd-4th day 



5 th day 





(18 hours). 



(18th-86th hour). 



(86th-108th'hour). 



per cent. 



c.c. 



c.c. 



c.c. 







25 



98 



12 



10 



17 



85 



1L 



20 



12 



85 



15 



50 



14 



. 79 





Conducted in dark room. Whole leaves, 17 grm., 4 hours after cutting in each experiment. 

 Cut at 3 p.m. Temperature of dark room 16*5-12 -5° C. C0 2 production estimated from, 

 increased pressures. 



