512 
Philippine Journal of Science 
1919 
ELEVATION 
Hevea brasiliensis appears to make its most rapid growth at 
low elevations. Though it has been grown in Ceylon and else- 
where at elevations up to 600 meters or more, the rate of growth 
is apparently much less rapid. It is probable that the retard- 
ative effect of altitude upon rubber is related to the lower 
temperatures prevailing at higher elevations. The extreme 
retarding effect of high elevations on the growth of trees in the 
Tropics is shown by the dwarfed condition of vegetation on 
mountain tops in these regions. 
Table IX gives the results of an experiment in Malaya to 
show the effect of altitude upon the growth of Hevea. While 
the small number of trees observed, especially at the higher 
altitudes, renders the results somewhat inconclusive, yet the 
experiment indicates a considerable reduction in the rate of 
growth as elevation is increased. The trees in clearing 8 were, 
however, said to be as healthy as those in clearing 1. 
Table IX. — Experiment on Gunong Angsi." 
Clearing. 
Elevation. 
Trees 
ready to 
tap. 
Total 
trees. 
Percent- 
age. 
Feet. 
Meters. 
1 
300 
91.44 
365 
.529 
69 
2 
600 
182. 88 
32 
180 
18 
3 
1,000 
304. 80 
321 
G65 
48 
4 
1,200 
385. 76 
(b) 
(b) 
(b) 
5 
1,600 
487. 68 
24 
90 
27 . 
6 
1,800 
574. 84 
17 
91 
18 
7 
2. 100 
640. 08 
66 
8... 
2, 400 
731. 52 
2 
90 
2 
^ From Agr. Bull, Straits & F. M. S. 10 (1911) 257. ^ Not planted. 
GROWTH IN THE PHILIPPINES 
It appears from the preceding discussion that climatic and 
soil conditions in the Mindanao region of the Philippine Islands 
compare well with those in regions in the eastern Tropics where 
plantation rubber is now being successfully produced. It re- 
mains to compare actual measurements of growth and yield of 
rubber of trees growing in the Philippines with those in other 
rubber-producing districts. In Table X a series of measure- 
ments is given of trees of various ages growing in the Philip- 
pines, and an attempt has been made to determine from these 
measurements the rate of growth of Hevea up to the age of about 
10 years. 
