1910. ] On Vegetable Assimilation and Respiration. 401 
the limit set by the temperature of 7° C.,and on raising the temperature 
the assimilation rose to 0°0252; the conditions of 1905 being thus repro- 
duced, the assimilation rose to a value which falls into line with those of that 
year in Table I. 
Experiment HE: Temperature the Limiting Factor—A second experiment 
similar to D was then carried out in order to get the limiting value for some 
other temperature. In this case the light was 5°7 and the COs-supply 0:0212, 
and at first the chamber was kept at a temperature of about 13° C. 
Fig. 6 shows that the assimilation kept at 00177 for three hours under these 
rs) 
(ea) 
b 
3) 
6 7 pin. 
at ohio On ihroughout 
Fig.6 Exp.€. 
conditions. At 4.30 p.m. the temperature was raised to 21° C., and then 
between 6 and 8 p.m. the assimilation increased to 0°0226, a low, but possible, 
value for the light as limiting factor, as Table I shows. 
The bearing of these experiments upon the problem of the nature of the 
limiting factor in the two long series in 1905 is clear. 
By Experiment D we have established 0°0115 as the “specific temperature 
maximum ” for the temperature of 7° C., and by E the value of 0:0177 for 
the temperature of 13° C. Assuming that assimilation in water-plants 
increases logarithmically with temperature, which can hardly be doubted on 
the evidence available for land-plants, we can from these two data calculate 
VOL. LXXXIII.—B. 26 
