1910. | On Vegetable Assimilation and Respiration. 399 
both of these factors being very high. In the first half the light intensity 
was only 4-2, being increased to 5°7 at 6 P.M. (fig. 4). The assimilation from 
4 to 6 PM. averaged only 0:0183, much lower than either CO,-supply or 
temperature would account for, and so it was expected that. the light was 
limiting. ‘This was proved in the second half of the experiment, because on 
increasing the light the assimilation rose, giving an average of 0°0220 between 
“O10 | 
“O00 | 
Temperature =~ 29°OC. 
Fig.4 Exp.C. 
7 and 9 p.m., which Table I shows us is a possible limiting value for the 
light of 5:7. 
We have attempted to prove directly that the average value of 0:0237 in 
the series on Table I is limited by light by starting an experiment in some 
of the conditions there shown and subsequently wereasing the light still 
further, in the expectation of getting still greater assimilation. 
There is, however, a difficulty about doing this, because rates of 
assimilation much higher than 0:0240 are not very long maintained before a 
decline sets in. This is a general phenomenon in assimilation which has 
