Vol. 6, 1920 
PHYSIOLOGY: H. S. REED 
407 
tions in the early part of the growth period are too scanty to give suffi- 
cient data for more accurate determinations. It will be noted that half 
of the observed values lie above the graph and half below it. This gives 
confidence in the reliability of the calculated values. The root-mean- 
square deviation of the 28 values is 2.78 cm. 
Table 5 gives the values of 5 in comparison with the computed values 
of dx/dt. S is computed from 
V2 [observed length at time (t + 1)— observed length at time (t — l)\. 
TABLE 5 
Values of S Computed from V2 [(Obs. Length at Time t + 1) — (Obs. Length at 
Time / — 1)] AND Values of --. 
at 
t 
5 
dx 
dt 
d 
t 
5 
dx 
dt 
e 
1 
20.7 
18.1 
-2 
6 
15 
7 
0 
6 
1 
-0.9 
2 
19.3 
15.6 
-3 
7 
16 
5 
0 
6 
0 
1.0 
3 
13.5 
13.5 
0 
0 
17 
3 
2 
5 
7 
2.5 
4 
11.7 
11.8 
0 
1 
18 
4 
2 . 
5 
4 
1.2 
5 
8.5 
10.4 
1 
9 
19 
6 
0 
5 
1 
-0.9 
6 
8.0 
9.3 
1 
3 
20 
6 
3 
4 
7 
-1.6 
7 
5.8 
8.4 
2 
6 
21 
5 
4 
4 
3 
-1.1 
8 
2.8 
7.7 
4 
9 
22 
4 
3 
3 
9 
-0.4 
9 
4.7 
7.3 
2 
6 
23 
3 
0 
3 
4 
0.4 
10 
9.4 
6.9 
-2 
5 
24 
2 
0 
3 
0 
. 10 
11 
10.3 
6.7 
-3 
6 
25 
1 
8 
2 
5 
0.7 
12 
8.4 
6.6 
-1 
8 
26 
1 
8 
2 
1 
0.3 
13 
6.7 
6.4 
-0 
3 
27 
1 
6 
1 
7 
0.1 
14 
6.5 
6.3 
-0 
2 
28 
0.7 
1 
5 
0.8 
If we use the values (5) which represent the slope of the chord whose 
mid-point corresponds to time, t, we shall obviate the minor fluctuations 
and get a more comparable expression of the observed rate of growth. 
McEwen and Michael (1919) have pointed out the usefulness of this 
method (p. Ill) which depends upon the fact that the slope of the chord 
of a simple curve is approximately equal to that of the tangent at the 
point midway between the extremities of the chord. The root-mean- 
square deviations of these values is only 1.91 cm., which indicates a 
satisfactory agreement. 
When these computations are translated into terms of the growing 
tree it appears that the growth rate in the early part of the season is high, 
but that it declines as the season advances. The rate of growth of the 
apricot branches indicates that the growth-impelling agency is at a maxi- 
mum at the beginning of the season and that it diminishes as growth 
proceeds. In the first seven or eight weeks the growth rate declines more 
rapidly than in any other period. From the eighth to the nineteenth 
