324 Mr. A. J. Wilmott. Experimental Researches on 



(C) Direct Comparisons of Soditcm Bicarbonate and Garhonic Acid loith the 



same Shoot. 



For the experiments in this section the rate ol bubbling was first taken in 

 CO2 solutions, and then the plant was transferred to a bicarbonate solution. 

 This sequence gives no risk of the readings in CO2 containing an injurious 

 after-effect of the bicarbonate solution. Fig. 16 shows the readings of the 



uJ 

 \- 



Z) 



z 



f 



CO 

 Ul ' 



CD ' 



00 



20 



40 minutes 60 



80 



ioo 



120 



20 



40 



A 



•\ 



"aro — 0-- 



.B 



\ 



\» 



V 



\ 



\ 



c 



» 



.. \ 



\ 



\ 



D 



s 



E 



I' 



t 

 1 



■A 



.9 4-5 

 1 



•1 4-0 



■ \ 3.0 



■ \^-^ 



V 



\ 



V 



: \ 





B 



\ 







c 



0--.. 







D 



■'^o — 0— . 







f/GUJ?£S 



JlaJte/i In 

 CO2 cund. 

 im. ^ 'uiojL- 



DmiuiLtes i'o 



— — . 



40 



B 



c ; 



% 



V 



\ 



80 



100 mlnatcs 



Fig. 16. — Bubble rates of Callitriche in six successive changes of solution. A, 0"6 per 

 cent. CO2 solution ; B, fresh 0'6 per cent. COo solution ; C, 0'2 per cent, solution 

 of NaHCOg ; D, fresh solution of the same concentration ; E, ditto ; F, 0'9 per 

 cent. CO2 solution. This last stronger solution was only employed to demonstrate 

 that the values A-E are none of them limited by light. 



Fig. 17. — Bubble rate of Callitriche. A, 0"6 per cent. CO2 solution, the plant being 

 observed for a long time in one solution instead of renewing the solution ; B, 

 0'08 per cent. NaHCOg solution ; C, fresh ditto. 



Fig. 18. — Bubble rate of Callitriche. A and B, 0'6 per cent. COg solutions ; C and D, 

 0*166 per cent. NaHCOg solutions. This record shows the irregularity that may 

 be got if the bubbler is not absolutely clean, so that some bubbles tend to stick 

 on to the bubbler and increase to an abnormal size before breaking away. In 

 such a case the resulting slow rates are neglected and the quicker values only 

 adopted. This sticking recurs in each solution of this experiment. 



first of these experiments. Each fresh solution shows its " initial CO2 

 diffusion effect," leading to the final value representing the static efl&ciency of 

 the solution. A and B give concordant values, 2-4 b.p.m. in 0"6 per cent. CO2, 



