Wombat Brush, at the two passes on
the great south road, over a great extent of country to the N.W. of Yass
Plains, and at Blackheath on the summit of the Blue Mountains. On the
other hand, those open grassy and park-like tracts, of which so much has
been said, characterise the secondary ranges of granite and porphyry. The
trees most usual on these tracts, were the box, an unnamed species of
eucalyptus, and the grass chiefly of that kind, called the oat or forest
grass, which grows in tufts at considerable distances from each other,
and which generally affords good pasturage. On the richer grounds the
angophora lanceolata, and the eucalyptus mammifera more frequently point
out the quality of the soil on which they grow. The first are abundant on
the alluvial flats of the Nepean, the Hawkesbury and the Hunter; the
latter on the limestone formation of Wellington Valley and in the better
portions of Argyle; whilst the cupressus calytris seems to occupy sandy
ridges with the casuarina. It was impossible that these broad features
should have escaped observation: it was naturally inferred from this, that
the trees of New South Wales are gregarious; and in fact they may, in a
great measure, be considered so. The strong line that occasionally
separates different species, and the sudden manner in which several
species are lost at one point, to re-appear at another more distant,
without any visible cause for the break that has taken place, will furnish
a number of interesting facts in the botany of New South Wales.

It was observed both on the Macquarie river and the Morumbidgee, that the
casuarinae ceased at a particular point. On the Macquarie particularly,
these trees which had often excited our admiration from Wellington Valley
downwards, ceased to occupy its banks below the cataract, nor were they
again noticed until we arrived on the banks of the Castlereagh. The
blue-gum trees, again, were never observed to extend beyond the secondary
embankments of the rivers, occupying that ground alone which was subject
to flood and covered with reeds. These trees waved over the marshes of the
Macquarie, but were not observed to the westward of them for many miles;
yet they re-appeared upon the banks of New-Year's Creek as suddenly as
they had disappeared after we left the marshes, and grew along the line
of the Darling to unusual size. But it is remarkable, that, even in the
midst of the marshes, the blue-gum trees were strictly confined