410 Dr. F. F. Blackman and Mr. A. M. Smith. [Dec. 19, 
of COs, the more rapid of his two rates, as sometimes the final rate is 
recorded as quicker than the initial.* 
> 
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bls 
3. 
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it 
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oO ELODEA 
= Data from 
o Pantanells 
=: 
Ter 
O00 MEECIO 020 7030. 040 <“D50° 0 =06ur 
CO, supply: grams per 100 C.c.of water 
Fie. 9. 
The data are not very regular, but it cannot be doubted that the diagram 
is of the same nature as our own fig. 1. Up to about 0-020 grm. COz per 
100 c.c. the assimilation increases proportionally with the CO2-supply ; then 
a limit is set by the 1/4 light-intensity, and the assimilation remains constant 
till about 0:06 grm. COz. After this the narcotic effect of strong CO, seems 
to begin, as bubbling in 0:065 grm. COz falls distinctly lower (this is just 
outside the range of our experiments in Section I). Further than this, as 
Pantanelli points out, the investigation cannot be pushed by bubble-counting 
alone as the physical liberation of CO. from the strong solution is so great. 
In this series, with intensity of light = 1/4, Pantanelli places the optimum 
at 0°02 grm. CO, (10 vols. COs per cent.)+; in a similar series, with 
1/1 light, at 0°63 grm. COs, and in the third series, with 4/1 light, at 
0-04 grm. COs. | 
We trust that our detailed consideration of Pantanelli’s work justifies itself 
* The bubble rate in “CO,-free” water (= 0°002 grm. CO, per 100 ce.) is impossibly 
high, but it is entered in the diagram; the rate in the strongest CO, (No. X) is 
obviously physical and erratic, and is omitted from the diagram. 
+ On p. 193 Pantanelli has an interesting footnote in which he treats with incredulity 
Treboux’s location of the CO,-optimum in his particular experiments at so low a value as 
about 3 vols. CO, per cent. This is obviously explained by the fact that Treboux used 
such a weak light (see p. 404), that the plant was inevitably prevented from utilising 
much CQ,. 
