( 223 ) 
clear an optimum which coincides with the 
maximum. The observations during 4 successive 
quarters of an hour very clearly indicate the 
logarithmic course of the falling-off, as is 
shown by fig. 4. 
We see from these figures that Blackman’s 
view as regards the optima, is also completely 
applicable to the respiration of Pisum. 
It remains to be considered whether 
Blackman’s theory can be applied still further, 
i.e. whether the value calculated according 
A ft ft 7 * hour to the rule of van t’ Hoff-Arrhenius, agrees 
Fig. 4. with that found by exterpolation. 
successive^quarter ^of an hour. Fig. 5 gives a representation agreeing com- 
pletely with that of Blackman 1 ). The abscissa indicates the tempe¬ 
rature, the ordinate the mgr. CO, liberated per hour. The line AF 
gives the figures found experimentally during the first hour of 
observation, while AB has been drawn by taking 2.8 as coefficient 
for a 10" temperature interval and considering the figures for 10°, 
15° and 20° as standards. The relation between the amount of CO, 
and the time would have to be indicated in a second plane at right 
angles to the abscissa. This plane has been imagined folded over to 
the right, for 40° over the line drawn at 40° perpendicular to the 
abscissa, and further for every temperature over a subsequent line, 
as the points B , C, and B always have an abscissa = 0 in this 
new system. From the point 40" onwards the abscissa indicates the 
time after which each observation was made. 
The values B—B t etc. have been taken from the table on p. 220 
The lines BB t , CC t and BB t are not smooth curves, so that the 
points B, C, and B may not be regarded as obtainable by exter¬ 
polation. On the other hand the greater or less inclination of the 
intervals BB lt CC X , and BB X agrees with the greater or less incUnation 
of the intervals B X B„ C X C 6 , and B x B t . 
The general impression which this diagram gives, is, in my opinion, 
that Blackman’s view holds good. Nevertheless, I consider that 
an important deviation is found in the impossibility of deducing the 
theoretical points from the other figures by exterpolation. A better 
analysis of the whole process by which CO, is set free, will perhaps 
some day explain this deviation. 
As was pointed out above, a falling-off is noticeable from 35 
*) Blackman, l.c. p. 284. 
