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675 
of that of the mangrove. In these places, as in the other situations, 
the Nipa-Acanthus formation is at the upper limits of high tide. 
Nearly all the species common to mangrove swamps which are found 
in the Indo-Malayan region, are also present in the Philippines, although 
not on the Reserve. 
(B) Mangrove formation at the base of cliffs—On the Lamao Reserve 
there are a number of shore promontories, at the bases of which wave-cut 
terraces have been formed, and some of these are thickly set with large 
bowlders offering a suitable place for the establishment of mangrove 
plants. The shore currents carrying the seeds or seedlings are likely, 
with the falling tide, to drop them in one of the interstices. The 
following species were noted geceras corniculatum, Sonneratia pa- 
gatpat, Ceriops candolleana, C. roxburgiana, Bruguiera eriopetala, and 
Avicennia officinalis. The presence in this strenuous zone of a dilute 
expression of the mangrove formation in protected patches conclusively 
shows that the main cause for their absence in the tidal area near sandy 
beaches is not due to the nature of the soil, but to the hydrodynamic 
forces there present. However, because of the nature of the habitat 
no closed mangrove swamps can be observed on wave-cut terraces; only 
isolated trees are here and there encountered. It is even possible that on 
more open coasts the protection afforded by the bowlders would not 
be sufficient to allow the invasion of such plants. 
Ecological characteristics of mangrove plants——Schimper ® has so 
thoroughly treated the peculiar characters of mangrove plants that here 
they need only be mentioned. They dre as follows: Prevalence of 
viviparous seeds, pneumatophores, stilt roots, and leathery, usually op- 
posite xerophytic leaves. 
The habitat—Undoubtedly, the main characteristic of the habitat is 
its salty nature and to this the peculiar formation is due. Whether 
other factors are operative in giving it this peculiarity is not known. 
It is possible that, for the edges at least, the reflection of the light from 
the water enhances the transpiration, but this would not be very effective 
for the shaded portions. Contrasted with the plants found on sandy 
strands, those of the mangrove swamps are undoubtedly obligatively 
halophytic. Observations extended over many miles of beaches show 
these forms to be only in salty, damp soils. It has been demonstrated 
that many plants growing on beaches are facultative xerophytes, but it is 
also true that many of them can also grow in salty soils and are therefore 
facultative halophytes. Copeland has shown that the coconut roots 
are, for a short time at least, adapted to resist salt water; whether they 
could withstand such soils permanently is not known. However, purely 
mangrove vegetation can not, for any length of time, exist outside of 
salty soils. 
° Loe cit., 396-406. * Copeland: Loc. cit., 17. 
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