certain Tropical Trees. 73 
The thermometers resting on the rows of red and green 
leaflets respectively gave at intervals the following readings : 
Thermometer resting on red leaflets = 32.7° C. 33-4° C. 34.4° C. 34-6° C. 34-4° C. 
„ ,, green leaflets = 31-9° C. 32-4° C. 33-2° C. 33-5° C. 33-3° C. 
Average temperature registered by thermometers : 
On red leaflets i= 33-9° C. 
On green leaflets = 32*9° C. 
The thermometers were tested by transposing them, and 
showed their accuracy very distinctly thus : 
Thermometer resting on red leaflets = 33-7° C. 34 0 34*2° C. 33-1° C. 
„ ,, green leaflets = 33.1° C. 33-1° C. 33 0 32-i°C. 
Average temperature registered by thermometers : 
On red leaflets = 33-8° C. 
On green leaflets = 32-8° C. 
In the second part of the experiment the thermometers 
were covered nearly up to the level of the mercury, one by 
the red, the other by the green leaflets. 
The thermometers now gave the following readings : 
Thermometer covered by red leaflets = 33-5° C. 33-3 32 31-6 32.3 33-2 32.1 
,, „ green leaflets = 35° C. 34.4 32.9 32.3 34 34-8 33-3 
Average temperature registered by the thermometers : 
That covered by red leaflets = 32*6° C. 
„ ,, green leaflets- 33*8° C. 
In short, when young thin red and older tougher green 
leaves of Amherstia are exposed side by side to the direct 
rays of the sun, the temperature, as registered by the ther- 
mometer, is higher to the extent of i°C. at the upper surface 
of the red leaves : conversely, of the temperatures registered 
at the lower surfaces of the leaves (i.e. behind them), that 
beneath the green is higher than that beneath the red, by 
a similar amount. 
Put in general terms, the surface-layers of the red leaf 
reflect more heat than those of the green leaf. The green 
