Photosynthesis : a Reply to Criticism . 
52i 
full temperature effect. In all probability it was the measure of a light 
effect. As will be seen from Fig. 7 of the paper in question, a temperature 
of 2 i° should allow of considerably more assimilation than was obtained 
at that temperature in either of the Expts. D or E. It was stated implicitly 
concerning Expt. D, and specifically of Expt. E, that the values obtained 
at 2 i° were light-limited values. Until Brown and Heise can bring forward 
proof that this was not the case, they are not entitled to use the results at 
21 0 in order to calculate therefrom a coefficient for temperature. 
It appears, therefore, from a reconsideration of the work of van Amstel 
and of Blackman and Smith that of the five coefficients given in Brown and 
Heise’s Table III, four are worthless because they are calculated from results 
in regard to which there is no proof that temperature was exerting its 
maximum effect. On the contrary, there is every probability that some 
other factor was limiting the intensity of the assimilation. The remaining 
coefficient, 2 * 05 , is perfectly sound and is of a magnitude which agrees with 
the van ’t Hoff rule. 
Brown and Heise’s Table III. 
Range of Temperature. Coefficient. 
7-13 0 2.05 
7-21 0 1.75 
13 - 2 I *35 
24-36.5° 1.28 
36.5-40° 1.25 
Calculated from data of 
Blackman and Smith, p. 402 
„ pp. 400, 401 
van Amstel 
>> 
The Work of Kreuster. 
Kreusler (1887) worked with one shoot of Rubus , kept in his chamber 
for three weeks and exposed to a different temperature every day. 
Matthaei (1904) showed that the activity of the shoot is declining day after 
day and that the material soon becomes quite unsound, so that it is impossible 
to analyse out pure temperature effects from it. At the end the shoot makes 
little response to change of temperature, while at the beginning it may make 
a large response. Brown and Heise, though aware of this criticism, welcome 
the results of the abnormal material as being nearer to their ideal of 1-04 
for the value of the temperature-coefficient. It hardly seems necessary to 
go further into this line of evidence. 
The Work of Matthaei on Cherry-laurel. 
The work of Matthaei (1904) on Cherry-laurel has been the chief 
experimental groundwork for the calculation of temperature-coefficients for 
carbon assimilation and has formed the chief support of the statement that 
such temperature-coefficients are in agreement with the van ’t Hoff rule for 
ordinary chemical processes in vitro. Brown and Heise make a detailed 
attack on Matthaei’s work, and it will therefore be necessary to consider 
somewhat fully their criticisms. 
