114 Sutton, A Sketch of the Keilor Plains Flora, [vd xxxiii 



where the creek valleys are wide, or where some hills have 

 weathered more than others, there are long, gentle slopes 

 which give a little relief to the general monotony of the 

 locahty. 



The water-courses draining the area are the Little River, 

 Werribee River, Skeleton Water-holes, and Kororoit Creek, 

 with independent outlets to the sea ; and the Maribyrnong or 

 Saltwater River, the Moonee Ponds, Merri, and Darebin Creeks, 

 emptying into the Yarra. All of these, in the fewness of their 

 tributaries, the steepness of their banks and hanging valleys, 

 furnish evidence of youthfulness, and the system contrasts 

 with the more mature state of that of the forest area on the 

 east and with the very ill-defined system of the coastal sands. 



The area under consideration is known as the Keilor or 

 Werribee Plains, or the basalt plains, and, while for some 

 reasons it might have been advisable to use the latter name 

 in designation of its flora, for others which seem better the 

 term "Keilor Plains flora" has been preferred. 



The vegetation of these .wide -spreading plains presents a 

 picture contrasting strikingly with the dense scrub-heath to 

 the south-east and with the forest formation lying between. 

 Inasmuch as it consists mainly of grasses mixed with low herbs 

 and shrubs, it is a grass-land formation, and, like the scrub- 

 heath and forest in their relation to the coastal sands and the 

 Silurian, it is found to conform closely to the basalt. It, in 

 fact, constitutes a quite distinct type of vegetation, exemplifying 

 a large part of the plant cover of the State. 



Before dealing in some detail with this plant formation and 

 its constituents, the principal conditions or factors which make 

 up the " habitat " or environment, and of which the vegetation 

 is the " reflex " or result, will be briefly considered. 



Climatic Conditions. 



Reference to the weather records shows that rainfall is lower 

 over the basalt than on the " sands " or the Silurian, and that 

 this is especially the case as regards the southern and larger 

 part of the area, where the fall averages only a little more than 



20 inches annually in about loo days. We find, for instance, 

 taking only stations where records have been kept for periods 

 longer than five years, that the figures are : — ^Altoria, 19.37 

 in 7 years ; Werribee, 20.19 in 33 years ; Little River, 20.01 in 

 25 years ; Bacchus Marsh, 20.93 in 26 years ; Melton, 20.90 in 



21 years ; and Keilor, 21.48 in 16 years. Doubtless there are 

 drier localities than these, as, not far outside the 30 miles radius, 

 Lara has 17.57 in 7 years, and Victoria Salines, near Geelong, 

 only 17.09 in 10 years. 



Over the northern portion, at more elevated stations, the 



