i^o Sutton, A Sketch of the Keilor Plains Flora, [vd.'^xxxiii- 



country were overwhelmed, leaving many intervening areas of 

 unsubmerged vegetation more or less widely isolated. These 

 islands were originally more numerous and smaller than now, 

 for, as the late Dr. T. S. Hall pointed out* in connection with 

 the country about Ballarat, the lava sheets were much more 

 extensive, and that particular surface of the bed-rock was 

 probably almost completely covered. When the basalt became 

 capable of supporting vegetation, the new surfaces began to be 

 peopled with plants from all sides, and the eastern drift was 

 resumed, the " endemic " species being evidently derived from 

 the nearest sources in the islands formed by the You Yangs, 

 Brisbane Ranges, the country between the Djerriwarrh and 

 Coimadai Creeks, the Lerderderg, and the high ground running 

 north-east to Macedon and beyond. 



Many thousand years must have elapsed since the surface 

 of the basalt became habitable to plants, yet Aster pimeleoides. 

 Pimelea elachantha, Brachyloma daphnoides, and Billardiera 

 cymosa in the vicinity of Bacchus Marsh, Acacia aspera in 

 the Brisbane Ranges, Heliptenim exiguum in the You Yangs — 

 to give only a few examples — ^have not been noted further 

 east. Epacris impressa, Isopogon cemtophyllus, Tetratheca 

 ciliata, Helichrysum ohcordatum (Lerderderg and Greensborough), 

 Eucalyptus camphora (Brisbane Ranges and Doreen), E. globulus 

 (You Yangs and Lower Yarra), and very many others occur 

 immediately on both sides, but seem to shun the basalt. Li 

 none of these plants is the power of invasion so very deficient 

 that it can be said for that reason to have failed to establish 

 itself on the basalt, and it must be assumed that either the 

 uncongenial nature of the substratum or the general unsuitability 

 of the habitat has prevented an advance. 



Whether the same species have failed to invade like basaltic 

 surfaces from other neighbouring formations it would be inter- 

 esting to know, and the matter might well engage the attention 

 of our members whenever opportunity comes to them. 



Very unequal progress has been made by those plants which 

 have already gained a footing. Eucalyptus Behriana and 

 Melaleuca parvi/lora, with the eremian Geococcus and Bassias 

 flourishing in their shade, have only just advanced across the 

 Djerriwarrh Creek. Claytonia volubilis and Calotis lappulacea 

 have been found no nearer to us than Anthony's Cutting : 

 Templetonia Muelleri and Acacia montana at Melton, and 

 Teucrium racemositm at Little River. Casuarina Luchmanni 

 is strung out from south of Parwan in a line running just east 

 of Melton and north to near the upper part of the Kororoit 



♦ " Victorian Hill and Pale," p. 151. 



