284 
Blackman . — Optima and Limiting Factors . 
We have now to apply the other method. Prolonged assimilation- 
estimations were made at high temperatures, the rate of falling off being 
determined at 30*5° C., at 37-5° C., and at 40-5° C. h In each case the 
estimations were four in number, of one hour’s duration each 2 , preceded 
by one and a half hours’ preliminary between the initial heating and the 
beginning of the first estimation. To plot these on the diagram we 
regard the base line as having only a time significance, each division 
1 See the experiments 58, 59, and 60 in Miss Matthaei’s paper. 
2 The numbers obtained for the ‘ real ’ assimilation (assimilation corrected for contemporaneous 
respiration) were as follows, in tenths milligramme C 0 2 per hour per 50 cm 2 . of leaf-area. 
c 3 = 157 
C 3 = 140 
C 4 = 129 
C K = 120 
E>2 = 237 
D 3 = 176 
D 4 = 139 
D 5 = 109 
E 2 = 147 
E 3 = 108 
E 4 = 98 
E 5 = 48 
The value for E* is clearly out of place, and the curve has not been made to pass through it. 
