{g"y] Sutton, A Sketch of the Keilor Plains Flora. 129 



Wilsonias. The most interesting of all the salt plants, and 

 named by Warming as a constituent of the Littoral Swamp- 

 Forest, is the white mangrove, Avicennia officinalis, only found 

 on the right bank of the Kororoit Creek, from near the race- 

 course to its mouth. It stands in tidal water just beyond the 

 bank, forming a thick, almost unbroken, hedge, and showing at 

 low water its myriad curious pneumatophores. 



Endemic Species. 



Comparing the Keilor Plains flora with the plants of adjoining 

 formations, it is found that more than eighty of its species are 

 endemic as far as the Melbourne district is concerned, and 

 most of these are known to occur more or less discontinuously 

 from the Mallee, in the north-west. The comparison also 

 reveals the facts that certain western plants, not recorded from 

 the east of the basalt, stop just short of it, and, further, that 

 very many flourish close to its borders on each side, but not 

 on the plains themselves. This discontinuity of distribution 

 lends special interest to these species, and calls for an ex- 

 planation, which, indeed, on a little reflection, seems obvious 

 enough. 



Judging from the opinions of Hooker, Wallace, Tate, Diels, 

 and others, it appears to be fairly certain that the vegetation 

 covering the south-eastern corner of Australia has been com- 

 posed of three or four elements. The first, perhaps, was 

 Antarctic in origin, derived through Tasmania from the south, 

 and now represented mainly by mountain and alpine forms. 

 Its influence on the flora of the basalt is quite insignificant. 

 With these mingled the Indo-Malayan from the north, and 

 eventually from the west, from the opposite south-western 

 corner of the continent — ^the home of the old original and 

 peculiarly Australian flora — the autochthonic plants drifted in. 

 This mixture of species from three main sources was also 

 augmented by invasions from the desert interior of eremian 

 plants, which, according to Professor Tate,* originate from 

 Indo-Malayan as well as from autochthonic ancestors. What- 

 ever the sequence of physiographic changes or order of arrival 

 may have been however, it seems extremely probable that long 

 before the era of volcanic action the western plants had already 

 established themselves, and that some of them had distribu- 

 tion and range greater than is the case at the present time. 



On the occurrence of the lava-flows, which the sketch mapf 

 shows having a general northerly trend, particularly along the 

 Goulburn, Campaspe, and Loddon Rivers, and filling in the 

 western part of the Great Valley of Victoria, large tracts of 



* Pr. A. A. A. Sc, 1888. f Vict. Nat., vol. xxxiii., p. 113. 



