xu,c,2 Brown and Heise: Carbon Dioxide Assimilation 91 
tion is reached at } sunlight, there is no real justification for so 
abrupt a change in slope as is indicated in the curve given by 
Blackman and Smith. 
These writers(3) take exception to the work of Pantanelli, 
because of the possible effect of temperature as a disturbing 
factor, as his work was carried out before Miss Matthaei had 
caused the great significance of this factor to be generally re- 
cognized. In a previous paper(4) we have shown that the 
temperature coefficient of carbon dioxide assimilation at the tem- 
perature at which Pantanelli performed his experiments (22° C. 
to 30° C.) is so small that the error, if any, introduced by neglect- 
ing to keep the temperature absolutely constant may well be 
disregarded. 
In the same paper we analyzed the results of Matthaei(14) on 
cherry laurel, and found that the relation between light intensity 
and assimilation might be expressed as a regular curve, similar 
in form to those of Pantanelli(16) and Reinke.(18) Matthaei’s 
results are shown in fig. 2. The agreement with the work 
previously discussed is particularly interesting, as Matthaei was 
experimenting with a land plant and made direct measurements 
of the carbon dioxide assimilated. 
Light intensity. 
40 20 30 40 
Carbon dioxide assimilation in milligrams. 
$a.8°-2s.2° ; 
Fic. 2. Relation between carbon dioxide assimilation and light intensity. Data of Matthaei. 
In reviewing the recent literature of carbon dioxide assimila- 
tion, Jorgensen and Stiles(9) lay considerable stress on the work 
of Blackman and Matthaei(2) as showing that there is a direct 
relation between carbon dioxide assimilation and various inten- 
