284 HARRIS, GORTNER, AND LAWRENCE: 
/700 
—--- 
S600 |- 
1500 }- 
x: 
~ 
. 
rw 
. % 
& 
1400 |- w 
ca 
i 
ro 
Bes 
1300 + 
Sai a 
1/200 |—- R oe 
1100 
a Height in Feet” 
10 20 ao > 40 $0 60 
DIAGRAM 4 
with a mean of — 112.3 for the negative differences. For all 
comparisons the mean differences in — 80.7. 
Thus our findings apparently indicate that if environmental 
heterogeneity plays a rdle in the determination of the differences 
in the physico-chemical constants found, the increased photo- 
synthesis at higher levels is the factor of the greatest importance. 
