The Girth Increment of Hevfe b^^sâiènsii» 
V 
BY 
T. FETCH, B.A., B.Sc. 
I N January, 1912, regular girth measurements on Hevea 
hrasiliensis were begun at Peradeniya as part of an 
investigation into certain phases of the physiology of the tree. 
It was not, however, found possible to carry out the investi- 
gation planned, but the girth measurements were continued ; 
and as few such measurements relating to the growth of trees 
in the tropics have been published, it has been thought 
desirable to place them on record. 
Sixteen trees were selected, eleven of which were seven 
years old, and the remaining five five years old. They 
formed three groups, of seven, four, and five trees, respectively. 
The trees of the first two groups were planted 20 feet by 30 
feet in tea. The first group consisted of seven consecutive 
trees in the same row on the same level. The second group 
was situated a short distance away, in a slight depression, 
about 6 feet below the level of the first group, the four trees 
standing consecutively in the same row. The trees of the 
third group were more closely, but irregularly, planted through 
cacao, the latter being planted at the same time as the Hevea. 
All three groups were within a distance of 200 yards. 
As numbered in the present account, trees 1, 4, 8, 9, 10, 11, 
12 constitute the first group, trees 2, 5, 13, 14 the second, and 
trees 3, 6, 7, 15, 16 the third. 
Measurements were taken weekly, on the same day each 
week at 9.30 a.m., and as the trees were being grown under 
ordinary estate conditions, they were taken at a height of 
6 feet from the ground, in order to avoid any errors due to 
the removal of the bark during tapping. A line was drawn 
on the stem at that height, and measurements were made 
along the line with a steel tape. 
When the measurements were begun, trees Nos. 1 to 8 were 
untapped, while the remainder had been in tapping for one 
Annals of the Royal Botanic Gardens, Peradeniya, Vol. VI., Part II., Nov., 1916. 
6(10)16 (11) 
