392 Dr. F. F. Blackman and Mr. A. M. Smith. [Dee. 19, 
Had a more intense light and higher temperature been fixed upon, then 
the ascending part of the curve would have been: prolonged further and 
a fixed (but higher) level only attained with a greater concentration of COs. 
With less light the limiting value would have been arrived at sooner. 
The second noticeable feature of this curve is the long range over which 
‘032 a Se 
i eel eee 
O24 
‘ Ral 
ie eee Se 
i seageeeeee 
O08 7 
O04 ; 
Assimilation 
grm C 
O24 
020 
Cay 
Bs Fenhinaie | 
- aoe 
[ a 
“COO 
0090 ‘O10 -020 030 “O40 *O50 -O60 
Mean COscontent of chamber in grm, CQ periooce water 
Fig.l 
the constant limiting value is obtained. There is no sign of super-optimal 
depression of assimilation even with the strongest solution used. 
In no previous experiments has the effect of such concentrated CO2 been 
satisfactorily investigated and it affords strong support to our view that the 
whole conception of an optimum is out of place here, to find no signs of it 
even with an environment as rich in CO2 as is an atmosphere containing 
30 per cent. of this gas. 
Of course with these aqueous solutions of COs, diffusion of this gas from 
