24 
The Queensland Naturalist 
May, 1932. 
THE PLANT ECOLOGY OF PALM ISLAND. 
(By Dr. D. A. Herbert, Department of Biology, 
University of Queensland.) 
(Continued from Vol. vii., p. 88.) 
(g) Braokisli Swamps. 
Towards the south-western corner where the low- 
lying flat cuts off the cape from the rest of the island, 
there is a fairly extensive peaty swamp. The water here 
is brackish, and a definite formation is developed. The 
dominant species is the paper-bark tea-tree — Melaleuca 
leucadendron — which attains a height of about thirty feet. 
At its base the peaty soil accumulates in heaps and the 
water lies round between the trees, leaving these small 
mounds projecting a few inches, or perhaps even one or 
two feet above the surface. Here and there are scrambling 
shrubs of Clerodendron inerme. The carpet flora consists 
almost entirely of ferns, the dominant species being 
Acrostichum aureum and Lygodium scandens, which climbs 
up the paper-bark trunks, forming a luxuriant lettuce- 
green mantle. Common also are Pteris ensiformis and 
Blechnum serrulatum. though these are not able to resist 
saline conditions as well as Acrostichum or Lygodium. As 
the swamp becomes more saline towards the sea, the tea- 
trees are replaced by mangroves — Avicennia officinalis 
(the Grey Mangrove), Bruguiera gvmnorrhiza, Rliizo- 
phora mucronata, and Aegialitis annulata. Lygodium 
disappears first, and Acrostichum persists right to the 
edge of the pure mangrove forest. Acanthus ilicifolius, 
which occurs on the inner edge of some mangrove forests, 
is found at the transition zone. 
Swamps of this type are found elsewhere on the west- 
ern side of the island, though of very limited extent. They 
are to be found fringing estuarine mangrove swamps. On 
the one hand they grade into mangrove forest, and on the 
other into open Eucalyptus forest. The pioneer tree 
of the open forest round such swamps is Pandanus. The 
ground covering at the edge of the Acrostichum is Cyperus 
polystachyus and grasses which (with the exception of 
Paspalum distichum) were not flowering at the time of 
the examination. Where fires have swept this transition 
area Heteropogon contortus has established itself. At an 
elevation of a few feet above the swamp and about thirty 
yards, from the outposts of the Acrostichum, the northern 
bloodwood (Eucalyptus terminalis) makes its appearance. 
Melaleuca leucadendron competes with the other members 
