264 
Pearsall.—Studies in Growth. 
variants were selected for each determination, the criterion being stem 
length. In this way, the plants remaining for the later determinations 
approximated more and more closely to the average of the material; the 
later determinations are probably more reliable, and their probable error is 
smaller. The probable error was not determined for the earlier readings 
(stem weight) in Series IV, V, and VI, since the individual weights are too 
small to measure accurately. 
Results. 
Series III was carried out at a temperature of 25 0 C. (+ 0-5°). In this 
an effort was made to obtain the complete growth curve and the results are 
recorded in Table II (Fig. 2). The figures for root growth show the 
characteristic stoppage of root growth previously recorded for roots on 
Tradescantia cuttings and for Broad Bean roots (volume measurements). 
The roots finally ceased growing about the ninth day, and no tertiary roots 
appeared either at this time or later (such as were found in Tradescantia). 
The stem at the ninth day, however, was growing at the maximum rate, and 
it was still growing at the conclusion of the observations. No marked 
increase in stem weight took place until the appearance of secondary roots, 
after which the elongation of the stem was very noticeable. 
Table II. 
Average Dry Weight of Peas (green wrinkled variety). 
Series III ( 25 ° 4 - 
i°C.). 
Series IV (15 0 
+ i°C.). 
Day . Shoot . 
Root . 
Day . 
Shoot . 
Root . 
1 
i*o mg. 
2-1 mg. 
4 
■ 1 -8 mg. 
9.8 ±0.39 mg. 
i -5 
i -3 
2-8 
4 s 
2-2 
io-i ±0-37 
2 
1.4 
4 -S + o-ii 
5 § 
3‘5 
10-7 + 0-40 
2-5 
1.9 
6-0 + 0-20 
5*2 
13.oio.42 
3 
3 -° 
7.4 + 029 
7 § 
7-6 + 0-40 
i 6 - 4 ±o -55 
3-5 
3 - 5±°-°4 
8-7 ±0-40 
9 
14-2 ±0-39 
2 i- 3 ±o -57 
4 
3-5 — °'°7 
1 1-2 + 0.32 
11 
25-o±o-52 
26-2 + 0-72 
4-5 
5 - 7 ±°- 3 o 
12-2 +0-71 
12 
31-0 + 0-77 
27.6 + 0-71 
5 
6-2 ±0.30 
12-4 + 0-47 
13 
35-7 ±°-79 
26-1 +0.90 
5*5 
7-610-35 
13-1 ± i-o 
14 
40-6 + 0-95 
26-610-83 
6-5 
12-7 ± 1-0 
16-1 + i-i 
16 
46-5 + I-IO 
27-8 + 0-71 
7*5 
18-4 + 1-2 
20-4 + 1.8 
8-5 
30.0 ± 2-4 
28.3 + 1.8 
9'5 
41.8 ± 2-9 
32-2 + 1-9 
10.5 
47-612-9 
3I-I + 2-0 
n -5 
52-0 + 3-2 
32-0 + 2-4 
Consideration of the rate curves for this series showed that prior to 
the appearance of secondary roots there seemed to be a negative correlation 
between the stem and root growth rates. When the stem rate increased 
that for the root decreased. After the appearance of secondary roots, 
stem and root growth both increased rapidly and roughly proportionately 
until the stem reached its maximum rate, when the root stopped growing, 
