502 ECOLOGICAL STUDY OP SALTMARSH VEGETATION. 



sion of the colony. The seeds of both species sank within 24 

 hours . 



Philydrum lanuginosum Bks., a succulent perennial which 

 ranges from China to Victoria, is common in the brackish pools. 

 Jt is also well represented in freshwater pools and swamps and 

 shows no appreciable alteration in either station. In the 

 shallows its growth is dwarfed, the tufts attaining their tallest 

 growth in permanent water 2—3 feet deep . The small seeds 

 sank within 12 hours. The Australian Violet, Viola hederacea 

 Labill., creeps on the banks of the pools or occupies the mounds 

 at the base of the Gahnia and Casuarina; Commelina cyanea 

 R. Br. trails over the low sedges and other herbaceous growths; 

 Goodenia paniculata has also a limited representation in this 

 station . The three above-mentioned species are preferably fresh- 

 water habitues. The Creeping Monkey Flower, Mimulus repens 

 R. Br., spreads a small mat of one to a few individuals on the 

 ridges in the saline area, occasionally invading the salt plain in 

 moist places. It was noted on the tide-flooded mud-banks in 

 Cook's River — an exclusive habitat — forming small patches. In 

 both stations the Mimulus is associated with Cotula reptans, also 

 a mud-creeper with a meagre representation. C. reptans estab- 

 lishes its largest formations in the coastal lagoons, Curl Curl, 

 etc., and is less tolerant of a freshwater station than its asso- 

 ciate. Limnanthemum geminatum Griseb., has a similar range 

 of salinity to Cotula reptans and is also common in the coastal 

 lagoons, a banded formation of this species occupying a distinct 

 zone on the shallow margin of the Narrabeen lagoon. A broken 

 colony was also noted in the less saline mud of a Casuarina 

 forest at Cronulla, its disintegrated membership evincing its 

 antipathy to the semi-aquatic habitat. That the reduced salinity 

 is not the cause of its weak growth is shown by the flourishing 

 colonies it forms in freshwater creeks and pools. 



Two species of Hydrocotyle, H. hirta R. Br. and H. asiatica 

 L., frequent the muddy depressions, but do not reach the salt 

 plain. H. hirta requires more moisture than its congener, dis- 

 playing a preference for a muddy habitat, the latter making a 

 more robust growth in a turfy lawn . Both are preferably 

 freshwater habitues. The Mullumbimby Couch, Kyllingia 

 monocephala Rottb., forms a close sward on the verge of the 

 pasture on the marsh boundary slopes where it is frequently 

 associated with H. asiatica; both species spread into the lawn, 



