402 Dr. F. F. Blackman and Mr. A. M. Smith. [ Dec. 19, 
the coefficient of increase for 10° C. The coefficient arrived at is 
1p = 205.7. 
We are now in a position to calculate the primary curve of assimilation 
and temperature in Elodea (see fig. 7, middle curve), and this will hold 
actually for medium temperatures. From inspection of this we see that the 
lowest temperature used in 1905, namely, 19° C., should allow an assimilation 
of at least 0:0267. The average limiting value obtained was, however, less, 
being 0:0237, so that though this is not much below the temperature limit 
it is Just enough so for us to consider it certainly proved that the light of 
57 intensity and not the temperature (19° to 23° C.) was the limiting factor 
in the 1905 series of experiments. 
The Inter-relation of these Limiting Factors—We will conclude this 
section by showing how the knowledge of the interaction of limiting factors 
on assimilation here set out will give us the power of predicting the value of 
the assimilation that will take place in any selected combination of the three 
external factors. 
Jnoy sed “os wb :uoiyejiwmissy 
oO a 
Ov) 
as 
a obo 
‘005 -010 
Fig. Tite eae of ee ras of ae and assimilation i in Blodea. 
Fig. 7 shows for Elodea the relation between different magnitudes of 
* This is nearly identical with the coefficient K,, = 2°1 arrived at for Cherry Laurel, 
Optima and Limiting Factors,” p. 283, 
