140 MUD ISLANDS, PORT PHILLIP BAY 



ently the most stable part of the region ; its outline and area have 

 not changed appreciably since 1860 (q.v. Admiralty chart). 

 Except for a few patches of blown sand facing the south-western 

 dunes across the lagoon, this area consists wholly of black mud 

 which is densely covered with Arthrocnemum arbuscidum 

 ("Shrubby Glasswort," to 5 ft.) — the dominant species — in var- 

 ious mixture with Suaeda niaritima, Atriplex palnclosa, Salicornia 

 austraUs, Framkenia pcmciflora and Samolus repens, the last 

 being abundant throughout. The salt marsh presents a rather 

 drab and monotonous aspect; the waterlogged soil, supporting 

 such a thick mantle of chenopodiaceous and other small shrubs, is 

 rich in organic matter. Again, in this community one misses 

 such characteristic halophytes as Disphyma australis, Pratia 

 plat yea! i/x and Selliera radieans which are common plants of the 

 salt marsh association in other parts of Port Phillip and in West- 

 ernport Bay. 



The ground is honeycombed with Storm Petrel burrows, where 

 patches of the marsh growth have been covered by drift sand, and 

 in these situations two weeds have taken possession: AnagaUis 

 arvensis ("Scarlet Pimpernel") forms an almost continuous car- 

 pet, while Cueumis myriocarpus ("Gooseberry Cucumber") is 

 also abundant and perhaps of more recent introduction — Campbell 

 did not observe it in 1906. The sole living, and very aged, tree of 

 Myoporwm insula re ("Boobialla") is to be found on this, Boat- 

 swain's Island, near a sandy rise; sprawling shrubs of Atriplex 

 einerea ("Coast Saltbush") also favour such higher parts of 

 the marsh, their branches often encrusted with the vivid orange 

 lichen Teloscliistes parietinus. 



3. Pained Shell Beds. 



Practically the whole eastern section of the group consists of 

 accumulated shells or shell-grit with a very sparse plant cover. 

 Isolated clumps of Atriplex einerea and A. patula (introduced 

 annual) comprise almost the entire flora in the north-east, i.e. 

 beyond Middle Island ; but at the south-eastern extremity, several 

 other annuals appear among the two saltbushes, viz., Pholiurus 

 ineurvus, Melilotus indica and Solicit as oleraceus. 



It is convenient to class with the shell-beds a few acres of guano 

 (formerly exploited) at the north-east, which carries an entirely 

 alien flora — doubtless the result of man's interference. The 

 dominant weeds here are Urtica urens ("Common Nettle" — very 

 abundant) and AnagaUis arvensis. Cerastium glomeratum and 

 the two grasses Poa annua and Vulpia hromoides occur in a very 



