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tide, showed this to be but 21.96 per cent. Reference to the table on 
page 426 will show this number to be less than one-half of that found 
for the clay soil of the interior. The sand which was tested had a 
humus content of 0.22 per cent, which is an exceedingly low figure; soils 
a few meters back of the situation from which these specimens were 
taken gave a considerably higher number, and consequently, their capacity 
to hold moisture is much better. 
The sand of the Lamao beach shows a remarkably high percentage of 
magnetite; in one sample, taken from near the mouth of the river, 76 
per cent of the total was composed of this mineral, although farther from 
the mouth, the percentage would probably be much less. 
The effect of the dry season on the vegetation on the beach is marked. 
During this period, trees such as Hrythina indica for a time shed their 
leaves and those of V'erminalia catappa and Barringtonia racemosa red- 
den and many of them drop before the new ones appear; the shoots of 
Ipomoea and other creepers partially or wholly die back and herbaceous 
weeds are nearly absent. Indeed, as a whole, during the season the thin 
appearance of the foliage is even more noticeable than it is in the 
Bambusa-Parkia formation. ‘The vegetative activity, after the initiation 
of the rainy season, is as rapid as it is on the clay soil; runners of Ipomoea 
and Canavalia grow with amazing rapidity and seedlings of Prosopis and 
other introduced trees in a short time form thick stands. During this 
portion of the year both exotic and native plants, derived from many 
habitats which are much less xerophytic, do surprisingly well in the 
forest nursery which has been established on the beach. The under- 
ground water level of the beach, 30 meters back from the sea, is a little 
over 2 meters below the surface and at the base of the cliff landward 
from the sea it is much less. The roots of the trees of the Barringtonia- 
Pandanus formation which I have examined, in a number of instances 
reached to this level and so they have a constant supply of water upon 
which to draw. Once the seedling stage passed, no tree having a deeply 
penetrating root system would suffer from a lack of soil moisture on 
such a beach. 
Another factor which is usually, and no doubt correctly, attributed as 
a cause promoting the xerophytic structure of beach plants, is strong 
light, because it increases the rate of transpiration. Copeland ** has 
shown that in Cocos nucifera the change from a light haze to full illumi- 
nation frequently multiplies the transpiration by four, and this is 
brought about by the fact that the leaf is heated above the temperature 
of the surrounding air. More light, and consequently more heat, reaches 
the leaves of plants on the beach than it does in the case of those situated 
in less sandy soils, because the reflection from the bright sand is greater 
* Copeland, E. B.: On the water relations of the coconut palm, Phil. Journ. Sci. 
(1906), 1: 35-37. 
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