320 Whitby . — Variation in Hevea brasiliensis. 
The girth data, like the data for latex strengths, appear to present 
a normal distribution. 
Correlation between Yield and Girth . 
The question of the extent to which the girth of the trunk is indicative 
of the rubber yield of a tree has considerable practical significance. If the 
correlation results showed that it is justifiable to assume that there is a high 
degree of probability that a tree with a small trunk will give a poor yield, 
and a tree with a large trunk a good yield, the work of selecting trees, in 
regard to their yielding capacity, for thinning-out operations would be 
greatly facilitated. 
The figures given below indicate that, although there is a definite 
positive correlation between yield and girth, the extent of the correlation is 
not sufficient to justify very much emphasis being placed on girth when 
selecting trees for thinning out. 
Table V. 
Correlation between Yield and Girth in a Popidation of ion Seven-year- 
old Hevea brasiliensis . 
Yields , grm, per diem . 
VO 
n 
<N 
VO 
00 
0 
vO 
<N 
n 
m- 
£>0 
| 
7 
7 
7 
7 
V 
T 
7 
S-< 
I 
1 
1 
CO 
m 
1- 
o\ 
WH 
ro 
10 
> 
O 
ro 
10 
i>. 
ON 
M 
1-1 
M 
N 
IN 
O 
50-52 
I 
I 
2 
53-56 
5 
3 
2 
I 
I 
12 
57-60 
8 
11 
3 
5 
I 
I 
29 
61-64 
>4 
15 
8 
6 
O 
2 
I 
49 
65-68 
13 
24 
16 
6 
3 
4 
2 
I 
I 
70 
69-72 
16 
30 
25 
l 1 
7 
5 
2 
2 
I 
I 
106 
73-76 
l i 
28 
19 
*7 
11 
H 
2 
2 
I 
2 
I 
114 
•77-80 
* 7 
36 
32 
2 r 
14 
11 
8 
4 
I 
I 
I 
146 
81-84 
16 
27 
29 
23 
8 
6 
5 
6 
2 
I 
2 
I 
127 
85-88 
13 
28 
21 
16 
8 
9 
5 
2 
5 
3 
I 
3 
114 
89-92 
8 ' 
17 
3 8 
19 
9 
6 
3 
1 
6 
1 
2 
1 
91 
93-96 
■5 
9 
10 
1 2 
S 
4 
1 
3 
1 
3 
I 
2 
1 
60 
97-100 
3 
8 
9 
4 
5 
6 
5 
3 
3 
1 
I 
r 
49 
IOI-X04 
2 
2 
5 
2 
2 
3 
1 
1 
1 
1 
20 
105-108 
3 
3 
1 
I 
8 
109-124 
1 
2 
2 
2 
1 
2 
2 
1 
1 
139 
241 
J 99 
T 54 
83 
7 i 
39 
22 
25 
9 
7 
7 
6 
9 
IOI I 
r = + 0.260 + 0.020. 
In addition to the characters which have been mentioned as showing, 
for a given tree, approximate constancy, certain peculiarities were observed 
in the cases of particular trees, which were also constant over considerable 
periods of observations, and which may probably be regarded as charac- 
teristic of the trees displaying them. Such were the following : 
(a) Rapid discoloration of the latex. Rapid oxidative discoloration of 
the latex may be associated merely with insufficiently deep tapping. Thus 
