498 ECOLOGICAL STUDY OF SALTMARSH VEGETATION. 



persal, the seeds of this Sedge forming part of the stomach 

 contents of Corcorax melanorhamphus, the White-winged Chough 

 (38, p. 94) . The seeds in an early stage of maturity are bright 

 red, changing when fully ripened to a dull brown. They are 

 shed from the glumes while still highly coloured and hang 

 temptingly suspended by the elongated staminal filaments. As 

 the colour fades, the shrinking filaments draw the seeds inwards 

 to the rachis. The red (unripe) seeds sank directly, the dry, 

 brown, fully-ripened seeds floating for several days. This giant 

 Sedge is present in the fluvial station in the saltmarshes and in 

 swamps and watercourses throughout the district. 



The only local species of either Gahnia or Cladium whose 

 fruits have more than a few days' flotation is Cladium jamaicense 

 Crantz, (Cladium (Gahnia) mariscus (F. v. M.) R. Br.), a cosmo- 

 politan species bsted by Guppy (13, 537) as having a flotation 

 of several months. Seeds tested by the writer were immersed 

 26th August, 1918, and are still afloat (28th June, 1919). 

 Though its fruits have every facility for dispersal by water, this 

 widely ranging species is indifferently represented in the Port 

 Jackson district. It is well established on the mudbanks in the 

 fresh waters of the upper reaches of Duck River and in the 

 broken headwaters of several arms of George's River at Oatley, 

 etc., and was collected at Cook's River by Mr. A. H. S. Lucas. 

 Its inadaptability is disclosed by its failure to spread along 

 the course of these rivers and colonise the numerous freshwater 

 swamps and lagoons with which they are more or less connected. 



Blechnum serrulatum Rich., a hardy fern which extends from 

 tropical America to the Malayan Archipelago, is frequently 

 associated with Gahnia psittacorum, erecting a limited brake on 

 the mounds at its base and raising its fronds above the flood- 

 waters on short rhizornatie trunks. When growing in a peaty 

 bog, the Blechnum usually chooses a station near the margin 

 where the surface is only occasionally flooded. In this habitat 

 the necessity for uplift is removed and the trunk formation is 

 discarded, the young fronds springing directly from the crown 

 of the tuft at the ground level. In some of the local bogs 

 the Blechnum has taken possession of this zone and extended 

 along the peaty margin in a broad band, restricted on the land- 

 ward side by the dry bank and regulated in the swamp by the 

 depth of water. An example of this banded formation occurs 

 at Maroubra Bay in the margin of the swampy lagoon at the 

 rear of the beach. 



