XIV , 0 Yates: Growth of Hevea Brasiliensis 503 
CLIMATIC CONDITIONS SUITABLE FOR THE GROWTH OF HEVEA 
The original home of Hevea brasiliensis is in tropical South 
America along the Amazon and its tributaries, a region having 
a moist warm climate, and a fairly uniform distribution of 
rainfall. Meteorological data from the observatory at Belem 
(Para), located near the coast and slightly south of the mouth 
of the Amazon, indicate a climate with a rainfall averaging 
about 2,500 millimeters fairly evenly distributed throughout the 
year, though with a dryer season during September, October, 
and November. The temperature appears to be fairly uniform 
during the year; it averages about 25° C., and rarely falls below 
20° C. or rises above 37° C. The distribution of rainfall by 
months and the number of rainy days in each month at Para 
are shown in Table I. 
Table I. — Rainfall at Belem {Para ) , State of Para, Brazil.’' 
[Rainfall is given in millimeters.] 
Month. 
ifl07 
190S 
1!)1<) 
Rainfall. 
Days. 
Rainfall. 
Days. 
Rainfall. 
Days. 
January.- 
208.9 
27 
295.8 
24 
262.4 
30 
February 
361.4 
27 
387.2 
26 
253.0 
26 
March 
234.3 
30 
219.3 
27 
404.6 
31 
April - 
174.6 
27 
349.4 
25 
246.5 
27 
May 
283.7 
28 
252.5 
27 
276.8 
23 
June 
242.7 
26 
132.5 
22 
333.0 
23 
July 
178.8 
24 
138.4 
14 
252.5 
19 
August 
133.8 
17 
117.6 
10 
153. 4 
22 
September _ _ 
81.8 
23 
89.9 
21 
101.1 
22 
October 
67.3 
IS 
93.1 
21 
76.6 
22 
November 
110.6 
22 
89.5 
18 
82.5 
22 
December 
260.1 
22 
163.2 
16 
282.5 
21 
Totals 
2, 338. 0 
288 
2,328.3 
260 
2,723.8 
287 
^ From Bol. do Museu Goeldi 7 (1910) 48. 
When a plant is introduced into new regions, it will usually 
be found to succeed best where the climate approaches that of 
its original habitat ; and this rule has been found to apply to Para 
rubber. The successful growth of Hevea is not strictly limited to 
regions where conditions are precisely similar to those prevailing 
in the Amazon Valley ; yet it certainly finds its optimum habitat in 
regions at comparatively low elevations, possessing a climate with 
a rainfall not much below 2,000 millimeters, evenly distributed 
throughout the year, and with a temperature rarely if ever falling 
much below 19° or 20° C., at least for any extended period. The 
