ae 
r = 
1910.] On Vegetable Assimilation and Respiration. AO7 
ten minutes is the proper time to allow for the chloroplast to readjust itself to 
a new set of conditions. For this there does not seem to be any real 
experimental justification in his work, and in his experiment on p. 182, 
where the plant continued 15 minutes in each light, the values continue to 
fall steadily for the whole 15 minutes. 
To us it seems that the better value to take would be the earliest value 
that is not subject to any special suspicion. The initial values recorded in 
each light-intensity are in all cases also the highest values, when the series of 
lights is an ascending one, and it is the initial values of bubbling that we 
have taken in the presentation of Pantanelli’s curve given in the inset 
diagram in our fig. 8. 
The first part of this curve is represented by a double track, because the 
experiments always began with the Elodea in light 1/1, and then proceeded by 
ten-minute stages down to light 1/36, after which the vessel, with its sprig of 
plant, is returned by the same stages to 1/1, and so on to 64/1. In further 
dealing with this curve, we propose to simplify this by taking the mean of 
the up and down series from 1/1 to 1/36 and back (see note to fig. 8). In 
such weak lights there is no injurious effect, and the plant returns practically 
to the same value for 1/1 as it started with. 
For lights 1/1, 4/1, and 9/1 the same initial value (within +2 per 
per cent.) is obtained in all three cases, afterwards the initial values begin 
to get lower and lower, not due to a primary optimal point having been 
passed, but to cumulative depression from prolonged exposure to intense 
radiation. 
If this is a sound point of view, one would expect that the high initial 
values would be kept up further along the series if the plant stayed a less 
time at each stage. Pantanelli’s own results show that this is so, for on 
p. 181 there is a small diagram of a set of experiments in which the plant 
stayed only three minutes in each position. Here the initial values up to 
36/1 are practically the same as at 1/1, and those at 49/1 and 64/1 
are only a little less. 
Even the curve of initial values, as modified in the inset to fig. 8, does 
not give the right aspect of the relation investigated, and this is due to the 
distorted scale of abscissz and ordinates adopted. 
It will be noted that from 4/1 to 64/1 the abscissze are proportional 
to the light-intensity, but for intensities below 1/1 down to 1/36 a 
logarithmic scale is adopted, which would put the zero of light at an 
infinite distance. Further distortion is produced by the fact that the 
ordinates do not represent intensity of assimilation (i.e. rate of bubbling), 
but the time taken by 10 bubbles to form, which is the inverse of the 
