MUD ISLANDS, PORT PHILLIP BAY 139 



live miles away to the west. Four distinct plant communities 

 are recognizable and will now be discussed briefly : 



1. Sand Dune. 



The long narrow Western Island consists of blown sand which, 

 on the northern and southern extremities, is piled into small but 

 stable dunes (to 12 feet high) supporting the only arboreal growth 

 in the area. Old be-lichened trees of Leucopogon parviflorus 

 ("Coast Beard-heath") at the northern tip form a tiny unmixed 

 woodland, some 8 or 9 feet tall — apparently the climax community 

 on dune sand. Seven different lichens and three mosses were 

 found on the trunks and branches of these venerable trees, beneath 

 which is an accumulation of leafy litter. The south-western 

 point not only supports a group of Leucopogon trees (fewer than 

 at the north end) but also the only occurrence (now) of Acacia 

 sophorae ("Coast Wattle") in the islands. 



Erect wiry Scirpus nodosus ("Knotted Club-rush") and herb- 

 aceous annual AnagalUs arvensis (the introduced "Scarlet Pim- 

 joernel") are conspicuous over much of this sand formation, also 

 such pygmy ephemerals as Sagina apetaia, Polycarpon tetra- 

 phyUum, Tortella calycina and Ceratodon purpureus (the last 

 two being mosses). Scirpus nodosus is an effective sand-binder 

 and has doubtless contributed to the stabilization of the dunes. 



The pioneer strand grass Spinifex Mrsutus was not noted any- 

 where here — a singular fact, as it is so abundant in many parts 

 of Port Phillip and outside the Heads, wherever cliffs give place 

 to a low sandy shoreline. Tetragonia expansa, Mesembryanthe- 

 mum aequilaierale, and Cakile maHtima are succulent species 

 mentioned in Mr. Mattingley's account as examples of the sand 

 dune vegetation; but I did not see any of these edible plants in 

 ]915 and suggest tbat rabbits may have been responsible for their 

 disappearance. 



There is evidence of some encroachment by the sea upon the 

 northernmost dune and its Leucopogon woodland, for dead trees 

 with bared roots are to be seen standing in the water at some 

 distance from the present dune face. It is most probable that 

 sucli erosion has exterminated at least three shrub species: the 

 dune composites Olearia axillaris, HcUchrysum cinereum, and 

 Calocepltalus Broivuii were recorded for the north-west on Camp- 

 bell's 1906 list, but I failed to find them after a careful search. 



2. Salt Marsh 



The low southern Boatswain's Island, "leg of mutton" shaped 

 and surrounded by shallow waters of the central lagoon, is appar- 



