90 
The Philippine Journal of Science 
1917 
In fig. 1 we have shown this relation graphically by plotting 
on plain coordinate paper the results given in Table III for 
light intensities up to full sunlight. The initial values and the 
values after 10-minute exposure are plotted separately for both 
the ascending and descending series. 
Light intensity (direct insolations 1.00) . 
Fig. 1. Relation between light intensity and bubble emission in Elodea. Results obtained 
with carbon dioxide concentrations of 1 to 15 volume per cent. From Pantanelli, Table IV, 
curve a. Curve a is for the initial values in the ascending series ; b, for values after 10- 
minute exposure in the ascending series ; c, for initial values in the descending series ; d, 
values after 10-minute exposure in the descending series. 
It is clear that the general form of the curve would be the same, 
whether any one series or the average for all series were con- 
sidered. There is no apparent reason for expressing the relation- 
ship as a straight line, as would be the case if the assimilation 
were directly proportional to light intensity. 
Pantanelli himself does not clearly state his opinion concerning 
the validity of a direct proportionality, but in his discussion of 
the results of previous workers he apparently assumes that such 
a proportionality does exist. 
In their analysis of Pantanelli’s work Blackman and Smith, (3) 
by using a small horizontal scale and drawing their curve in an 
arbitrary manner, obtain a straight line for lower light inten- 
sities, and from this they conclude that 
From intensity to % [sunlight] the assimilation increases in direct 
proportion with the increase of light and then a limit is reached. 
The fallacy of this reasoning is apparent from the form of the 
curve in fig. 1. As there is no indication that a limit of assimila- 
