278 WILLIS : MOEPHOLOGY OF THE PODOSTEMACBÆ 
Total 147*60 on 193 clays. Greatest fall in 24 hours 1T40 
inches. [If a coefficient of about 25-30 be added to these 
figures, they may fairly represent the average level, e.g.^ 
28-33 in January and 50-55 in June.] 
It will be observed that there are two seasons in the year, 
each of about six months’ duration, corresponding to the two 
monsoons, beginning with much rain and gradually becoming 
drier. The north-east monsoon begins about the middle of 
October, and there is much rain until about Christmas, with 
high water-level in the rivers. The rocks seen in the 
photograph of Hakinda are very commonly all submerged at 
this time, though the rapids are about 200 metres wide. 
About the end of the year the rainfall slackens, and the dry 
weather of this monsoon, the “ dry season ” of S.W. Ceylon, 
sets in. The Podostemaceæ, lately deeply submerged, now 
become graduallj^ exposed to the air as the level of the water 
sinks, and as they become exposed, the flowers, which are 
quite ready for anthesis, open, become fertilized, and quickly 
ripen their fruits, shedding the seeds upon the dry rocks, 
while the old plants usually die. In this condition they 
remain until April, when the south-west monsoon begins, 
with gentle winds and a good deal of rain. This first onset 
of the monsoon is not violent, and is locally known as the 
little monsoon,” but there is usually enough rain to raise 
the water-level so high that all the seeds germinate. A fall 
of water-level takes place in May, at which time it is usually 
practicable to get at the plants once more and to search for 
seedlings, and then about the end of May the “ big ” monsoon 
sets in with violent wind and rain from the south-west, 
causing the river to rise very high. During June and July 
it usually remains high, but in August and September there 
is usually less rain, and the level of the water sinks, of ten so 
low as to expose some of the plants to the air. If this 
happens the exposed parts of the plants usually die unless 
quickly re-submerged, and they have not yet developed their 
