October, 1930 The Queensland Naturalist 
87 
THE PLANT ECOLOGY OF PALM ISLAND. 
By Dr. D. A. Herbert, Department of Biology, 
University of Queensland. 
(Continued from Yol. VII., page 72.) 
Grassland. 
Behind the strand, and a little to the south of the 
tidal creek which meanders through the plain enclosed 
by the horse-shoe range to the north of Challenger Bay, 
are a few acres of what is apparently original grassland. 
This area is sandy and gently undulating, On the rises 
a few trees of the northern bloodwood (Eucalyptus ter- 
minalis) are established, giving a savannah formation with 
Cycas sp. forming the second story. In hollows where 
the water is held the grassland gives place to a Melaleuca 
leucadendron — Phragnutes communis swamp association. 
The composition of the grassland is very uniform and con- 
sists of an almost pure consocies of Anthistiria imberbis. 
An occasional plant of Heteropogon contortus is found, 
and a count showed that the individuals of the two species 
were in the proportion of 200 : 1. Anthistiria is shallow 
rooting, and none of the plants examined had formed any 
seed, though they had flowered abundantly. This grass 
is very readily suppressed, therefore, by firing, the whole 
plant being killed and practically no seed being present to 
re-colonize the burnt-over area. Heteropogon, on the other 
hand, is deep-rooting and has an abundance of seed, and 
after the firing of this grassland becomes established as 
the dominant species. An enemy of the kangaroo grass, 
second in importance to fire, is Cassytha filiformis, the 
Bush Dodder, which destroys it along the -sh-ore, and 
gives an advantage at this point to low strand plants such 
as Cenchrus echinatus, the Burr Grass, and Vitex trifolia. 
Another type of grassland is found where the forest 
has been burnt over. On Great Palm Island the burning 
of the forest results in a clearing of the shrubs and herbs, 
but the trees are generally left, except at the edges of the 
monsoon forest, which is particularly sensitive to fire. 
Along the margins of the monsoon forest in such cases 
will be found a treeless strip, which has become colonized 
by tall grasses. These persist through the open Eucalyptus 
forest, but of course are not pure grassland in this case. 
Four grasses are found commonly — Heteropogon contor- 
tus, Panicum trachyrachis, Stipa semibarbata, and Anthis- 
tiria imberbis, the latter very scattered. The three 
former are tail grasses and form dense thickets three to 
five feet in height. Panicum trachyrachis occurs through 
the Heteropogon, but Stipa more usually forms commun- 
ities several yards or more in diameter, or strips along the 
