IN THE TROPICS. 
361 
observing the behaviour of the more definite characters on 
crossing. 
CLIMATIC CONDITIONS—ACCLIMATIZATION . 
The most important differences in climate between different parts 
of the year in Ceylon depend espècially upon variations in the 
amount of precipitation. Thus a general idea of these differences, 
so far as they affect the growth of plants, may best be obtained 
from a table of the monthly rainfall. Such a table is given below, 
and covers the period during which the work in Ceylon was 
carried on. 
Rainfall at Peradeniya in Inches, and Number of Rainy Days. 
1902-1903. 1903-1904. Average 21 years. 
Rain. 
Days. 
Rain. 
Days. 
Rain. 
Days. 
September 
9-00 
17 
11-36 
27 
6-86 
16 
October 
.. 25*15 
28 
13-73 
24 
14-00 
20 
November 
.. 17-43 
22 
2-71 
13 
10-86 
17 
December 
7-46 
18 
10-20 
19 
8-44 
13 
January 
2-69 
8 
11-20 
19 
3-32 
7 
February 
1-86 
8 
1-87 
4 
1-59 
4 
March 
•14 
2 
3-55 
7 
4*52 
8 
April 
6-88 
11 
3-54 
9 
9-59 
14 
May 
.. 12-33 
17 
9-90 
17 
6-95 
12 
June 
5*74 
17 
18-98 
30 
10-43 
20 
July 
7-36 
27 
11-71 
29 
7-87 
19 
August 
313 
17 
3-70 
12 
5-75 
17 
The above table may be left to tell its own story. As regards 
temperature, the mean is very uniform all the year round, ranging 
from about 74° F. in January to 78° F. in May. The difference 
between the maximum and minimum temperature is greater in dry 
weather than in wet. Thus the greatest daily range of temperature 
occurs in January or February, at the beginning of the relatively dry 
season terminating the north-east monsoon, when the difference 
between day and night temperatures may be as much as 25° F. The 
smallest range is recorded during the wet weather of the south-west 
monsoon in June and July, when the average difference between 
maximum and minimum is about 10° F. 
