MOUNTAINS AND THEIR EFFECT ON NATIVE VEGETATION. 277 
and drier west. In this latitude, about 35°, there are few 
western plants which thrive at elevations exceeding 2,000 
feet. 
The Cassilis Geocol, in about latitude 32°, is only from 
1,700 — 2,000 feet above sea level, and there are higher 
mountains to the eastward, both north and south of 
Singleton, which have the effect of shutting off the coastal 
influence from a fairly large area to the westward, between 
these mountains and the low portion of the Main Divide 
near Cassilis. The result is that it isthe descending clouds 
which reach this isolated area, and the rainfall, which on 
the coastal side of the mountains opposite this point is 
upwards of fifty inches annually, is less than twenty-four 
inches in the geocol area. There are many plants in the 
western districts occupying zones which reach up to eleva- 
tions of 1,800 feet in latitude 32°, and it is easily seen 
that in following their upper contours along the western 
side of the Main Divide, these plants on arrival at the broad 
gap are able to pass through on to the eastern watershed, 
seeing that from this particular locality the coastal moisture 
has been largely excluded, and the climatic conditions are 
more Similar to those of the western than the eastern side 
of the main mountain range.? 
Part of the Liverpool Range, however, as it winds round 
north-easterly towards Murrurundi, and forms the north- 
western side of the geocol, rises to elevations of about 
3,000 feet, and receives a greater rainfall from the ascend- 
ing clouds, with the result that the heads of the gullies 
which face easterly and are sheltered from the colder and 
drier westerly influence are filled with brush, and when 
viewed from the lower open forest areas within the geocol, 
present a magnificent example of the effect of topography 
on the native flora. 
* A list of the plants which have crossed is given in the New South 
Wales Handbook, p. 418, Cambage and Maiden. 
