The Controlling Influence of Carbon Dioxide. 



143 



Table V.— Showing that Normal Kespiratory Activity is Eesumed after 

 Removal of Retarding Concentrations of Carbon Dioxide. 



Initial CO., 

 in N 2 . 



C0 2 production. 



Seeds used 

 germinating 

 finally in air. 



(Anaerobically) in 

 atmospheres of N 2 con- 

 taining various partial 

 pressures of CO L >. 



(Anaerobically) 



in nitrogen 

 replacing former 

 atmospheres in 

 each experiment. 



(Aerobically) 



XXX (VLL X C |.'ltX vlll j£ 



former atmo- 

 spheres in each 

 experiment. 



21 lirs. 



36 lirs. 



45 lirs. 



21 hrs. 



43 hrs. 



Germination, 

 per cent. 



per cent. 



c.c. 



c.c. 



c.c. 



c.c. 



c.c. 









33 



49 



68 



26 



97 



92 



10 



29 



39 



51 



31 



103 



96 



20 



22 



32 



46 



27 



99 



76 



50 



18 



29 



38 



24 



90 



92 



Conducted in dim diffuse light. In each experiment, 25 peas with lestas, 8 grm. dry weight, 

 set dry with 12 c.c. distilled water. 



Anaerobic C0 2 production estimated from pressure increases, aerobic from analyses. 

 Temperature of experiments 20° C. thermostat. 



Peas sterilised in 1/500 bromine for half an hour. Flasks were also sterilised with bromine 

 solution. 



These experiments make it clear that the results so far obtained cannot be 

 regarded as clue to a permanent injury produced by the increased concen- 

 trations of carbon dioxide used. Thus it is seen in Table IV that, while the 

 amounts of carbon dioxide produced by the respiring seeds under the 

 influence of rising percentages of CO2 form a falling series in some inverse 

 relation to these rising concentrations, yet when subsequently the increased 

 percentages of CO2 are removed and the conditions in all the experiments 

 equalised, the amount of C0 2 respired by the seeds in each then returns to 

 an equality, as the figures in the sixth column of the Table will show. The 

 conclusion is reached, therefore, that the effect of increased concentrations of 

 C0 2 in the atmosphere is to reduce the CO2 production in aerobic conditions 

 without destroying the potentiality of the process returning to the normal 

 on the removal of the retarding CO2 pressures. 



This conclusion being established in its general aspect, it is now of interest 

 to examine our results more in detail and quantitatively. In fig. 1 the 

 results of the series of experiments given in Table IV are shown 

 graphically, so as to bring out the depressant action of C0 2 . The curves 1-4 

 represent total C0 2 evolved in cubic centimetres after 19, 31, 51, 90 hours 

 respectively as influenced by the concentration of C0 2 present. Each 

 vertical series of points comes from one experiment. In plotting these, 



