BY A. A. HAMILTON. 497 



Bramble. When this station is reached their respective bound- 

 aries will be regulated by the fluctuating water supply. The 

 Bramble is incapable of building a thicket sufficiently high for 

 the suppression of the taller Melaleucas, but if left undisturbed, 

 will eventually displace them, its close investment preventing 

 sexual reproduction — their only means of renewal — as no seed- 

 lings could survive in the Bramble thicket. The investment by 

 the Bramble also operates unfavourably to the Casuarina, whose 

 seeds, though provided with a wing, are not, as previously 

 shown, adapted for a lengthy flight. 



The Chinese Box-thorn, Lycium Chinese Mill., is represented 

 in the Casuarina forest by a scattered colony, discarding in this 

 station its customary chapparal growth. At Lady Robinson's 

 Beach, the Box-thorn has demonstrated its halophytic tendencies 

 and exposure-resistant capacity, by extending in belted forma- 

 tion along the verge of the frontal embankment of the dune. 

 Its hardy growth and divaricate habit have encouraged its culti- 

 vation as a hedge plant, but its adaptability has, in many places, 

 destroyed its usefulness as it has spread over the pastures and 

 is difficult to eradicate. 



The undergrowth in the muddy fluvial station in the Casuarina 

 forest is largely herbaceous, the dominant species responding to 

 the xerophytic conditions, lack of aeration and acidity, by the 

 production of leaves and stems with a fibrous or leathery tex- 

 ture. The keenest competition in this station occurs among the 

 low growths in the flooded depressions, the taller plants usually 

 forming loose clumps, or occurring as isolated individuals, on the 

 slightly elevated ground surrounding the depressions. Several 

 species have developed a trunk-forming habit with the object of 

 raising the crown of the rootstock — from which the tender young 

 shoots emerge — above the level of the occasional flood-waters. 

 Of these the most prominent is a giant Tussock-forming Sedge, 

 Gahnia psittacorum Labill., endemic in the Commonwealth, which 

 erects a mound at its base, its bulky rhizomes, whose twisted 

 arms arise and project in every direction, obstructing and re- 

 taining debris from the passing flood. These mounds form a 

 special habitat and are occupied by a few selective minor herbs 

 whose requirements are a rich permeable soil with a constant 

 supply of moisture. The distribution of G. psittacorum is the 

 work of birds, chiefly Parrots, as the specific name indicates, 

 though other birds are in some measure responsible for its dis- 



