88
WILLIAM MACNAE
or less permanently waterlogged soils. The barringtonia racemosa
association occurs on relatively well-drained soils which may show a
seasonal water-logging.
The first three of these associations occur only on sheltered shores ;
the fourth is equally characteristically found on open wave-beaten
shores. Members of the pes-caprae association are often useful dunefixing agents.
To these four associations it may be convenient to add a fifth
association which occurs from mean sea-level downwards, on sheltered
;hores or in rock pools on open shores.
(e) The Cymodocea Association-dominated by one or other of the
species of Cymodocea intermingled with species of Diplanthera,
Enhalus, Halodule, Halophila, Syringodium, Thalassia and
Zostera.
Again this association does not really concern us except as it may
occasionally encroach on the lower zones of the mangal.
Schimper (1891) was dealing only with the plant associations in the
region between India and western Indonesia, drought-stricken areas
did not come within his survey. When evaporation comes to exceed
the availability of fresh water Schimper’s first three associations
become highly modified. The nypa and barringtonia racemosa associations become less and less conspicuous and in their stead occurs :
The Saltwort Association-dominated by bushes or low shrubs
of species of the perennial Arthrocnenum and the annual
Xalicornia.
When evaporation becomes excessive, bare areas devoid of any vegetation supervene, and then all plant communities are restricted to the
vicinity of creeks, occasionally with a fringe of halophytes around high
water mark.
I n summary, one may recognize on Indo-west-Pacific shores above
the level of high water of neap tides, two basic plant associations.
( 1 ) Just above high water mark of ordinary spring tides there occurs
on exposed shores or sandy shores the lpomoea pes-caprae
Association, and this with only a few of the associates varying,
extends from semi-desert shores t o the ever-wet, where rain
may fall abundantly at all seasons. I n the humid tropics this
may be associated with a Barringtonia asiatica Association.
( 2 ) On sheltered and muddy shores, the Mangal stretches from near
mean sea-level upwards to extreme high water mark. As
variants a t higher levels we may find (a) a Nypa Association,
(f )
WILLIAM MACNAE
or less permanently waterlogged soils. The barringtonia racemosa
association occurs on relatively well-drained soils which may show a
seasonal water-logging.
The first three of these associations occur only on sheltered shores ;
the fourth is equally characteristically found on open wave-beaten
shores. Members of the pes-caprae association are often useful dunefixing agents.
To these four associations it may be convenient to add a fifth
association which occurs from mean sea-level downwards, on sheltered
;hores or in rock pools on open shores.
(e) The Cymodocea Association-dominated by one or other of the
species of Cymodocea intermingled with species of Diplanthera,
Enhalus, Halodule, Halophila, Syringodium, Thalassia and
Zostera.
Again this association does not really concern us except as it may
occasionally encroach on the lower zones of the mangal.
Schimper (1891) was dealing only with the plant associations in the
region between India and western Indonesia, drought-stricken areas
did not come within his survey. When evaporation comes to exceed
the availability of fresh water Schimper’s first three associations
become highly modified. The nypa and barringtonia racemosa associations become less and less conspicuous and in their stead occurs :
The Saltwort Association-dominated by bushes or low shrubs
of species of the perennial Arthrocnenum and the annual
Xalicornia.
When evaporation becomes excessive, bare areas devoid of any vegetation supervene, and then all plant communities are restricted to the
vicinity of creeks, occasionally with a fringe of halophytes around high
water mark.
I n summary, one may recognize on Indo-west-Pacific shores above
the level of high water of neap tides, two basic plant associations.
( 1 ) Just above high water mark of ordinary spring tides there occurs
on exposed shores or sandy shores the lpomoea pes-caprae
Association, and this with only a few of the associates varying,
extends from semi-desert shores t o the ever-wet, where rain
may fall abundantly at all seasons. I n the humid tropics this
may be associated with a Barringtonia asiatica Association.
( 2 ) On sheltered and muddy shores, the Mangal stretches from near
mean sea-level upwards to extreme high water mark. As
variants a t higher levels we may find (a) a Nypa Association,
(f )