MUD ISLANDS, PORT PHILLIP HAY 1-11 



depauperate condition, while the rock-like guano itself is covered 

 by the crustaceous lichens Lecanora umbrina and Ccmdelariella 



vitcllinci. 



4. Sh allow Walcr. 



In the lagoon and shallows, especially at the northern end of 

 the group, is an association of aquatic phanerogams consisting 

 for the most pari of one species, Zostera muelleri (" Dwarf Grass- 

 wrack") — the food of water birds. Z. tasmanica also occurs at 

 the north and, apparently, Halophila oralis in deeper water, 

 though I did not see it. 



General Notes 



In addition to the four well-defined communities just mention- 

 ed, one can distinguish certain transitional elements along their 

 respective borders — e.g. Stipa teretifolia of the dunes occurs 

 sparingly on raised shell beds, while Atriplex cinerea of the latter 

 formation enters the dunes; Suaeda maritima and Salicornia 

 Blackiana migrate from their typical marsh habitat out on to the 

 shelly beds, the latter species appearing to favour drier ground 

 than its congener Salicornia australis: the three weeds Urtica, 

 A nagallis and ( 'ucumis, while more abundant on guano, also extend 

 out into the dunes. It would he interesting to tabulate 1 he occur- 

 rences of all these species again after another period of, say, 40 

 years and note any changes in local distribution. Indeed, the Mud 

 Islands, so circumscribed and relatively free from interference, 

 would form an admirable subject for a detailed ecological survey. 



Chenopodiaceae is by far the largest natural assemblage, both 

 in species (8) and individuals; this family and the Gramineae (5 

 species) together account for 43 per cent of the islands' original 

 flora (30 spp.). The number of indigenous species per genus is 

 11, and of species per family 21. (KB., Dr. R. T. I'atfon also 

 obtained the former figure in his studies on Salt Marsh flora — q.v. 

 Proc. Royal Soc. Vict. LVI, p. 134, 1942). Systematically, the 

 naturalized alien plants now constitute exactly a quarter of the 

 flora, but none of the ten species seems to he aggressive or likely 

 to threaten the existence of any plants native to the area. 



Extensive sand hanks with wry shallow water arc not con- 

 ducive to a rich algal flora and, indeed, the shores of Mud Islands 

 seem deficient in marine algae. The attractive calcareous Acetabid- 



aria peniculus was noted (washed ashore on the hacks of shells), 

 also several Caulerpa species; hut no attempt was made to cata- 

 logue any marine algse for this small area. 



