482 
Darwin . — On the Growth of 
Fig. 9 shows a steady rate of growth at an intensity less 
than the rates at 1 p.m. and 6-9 p.m. in Fig. 8. The brighter 
weather at noon is clearly represented in the parallel disturb- 
ance of the two curves. On the other hand the fall in growth 
rate at 2.37 is not accounted for by the state of the air. 
Fig. 10 shows a fairly uniform rate of growth at night — and 
a rise in rate in the morning in spite of the increased dryness 
of the air. This rise I believe to be due to the plant having been 
watered at 9.1 5 - The disturbance in the curves at noon is 
due partly to alternations of sun and cloud and partly to the 
syringing of the leaves. There is no marked evening rise in 
spite of the rise in the humidity curve. 
Fig. 11 is chiefly remarkable for the nocturnal fall in growth. 
The nocturnal temperature fell lower than usual ; but this 
will not account for the fall, since between 1 a.m. and 3 a.m. 
the curve rises with a constant low temperature. 
In none of the above-described figures is there any evidence 
of the change from night to daylight producing an effect. 
Exp. 18 is given as a whole in Fig. 12, where the rate of 
growth is calculated for intervals of three hours, and expressed 
as o*ooi mm. per minute. 
Omitting the violent temporary rise on the evening of the 
1 5th, it is clear that the rate of growth is gradually sinking. 
In spite of considerable irregularity, the temporary evening 
rise is fairly visible, as is the fact that the rate of growth is on 
the whole stronger by day than by night. The difference, 
however, is not marked : in the following table the rate of 
growth has been calculated for the night and day, taking the 
nearest available hours to 6 p.m. and 4 a.m. ; that is a night 
of 10 hours and a day of 14 hours. 
July 12 
» 13 
mm. o-oi per hour. 
6 p.m. 
4 a.m. 
6 p.m. 
3.50 a.m. 
5 P* m * 
3 a.m. 
5 p.m. 
43 
37 
26 
20 
21 
23 
