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poisonous to all ruminants prevents any attempt at systematic 
overstocking 
Originally the gorge of the Lower Murray was well-covered 
with herbaceous plants and grasses, which were confined to the 
actual banks of the river and to the lagoons, some of which are 
two to three miles long, and one to half a mile across. Here the 
“lionum” (Muehlenbeckia Cunninyhami), attained its largest 
growth, 15 to 20 feet high, and so thickly matted together as to 
be impenetrable ; but at the present time, many miles of this 
valley have been denuded of lignum, reeds, bulrushes, and grasses, 
and the prevailing aspect is an uninteresting expanse of dry mud 
and sand, only diversified by a few Eucalypts. The destruction 
of the swamp-vegetation throughout Riverina has considerably 
lessened the amount of stock which formerly grazed upon it 
during the long hot summers and during droughts. 
No class of country suffers so extremely from excessive stocking 
as the sand-hill country, and especially the sand-dunes which 
fringe much of the coast-line of Southern Australia. As natural 
growth is exterminated, the sand, no longer protected by the 
herbs and shrubs shading its surface, and binding it together with 
their very long and widely-spreading roots, is driven by the pre- 
vailing winds over the surrounding country, to the destruction of 
all lowly vegetation; even forest-trees are overwhelmed in the 
advancing sand-waves. This phenomenon is not confined to the 
coast-line, but instances, usually on a limited scale, may be found 
in the interior. 
The destructive effect by stock trampling down and consolidat- 
ing the clay-surfaces around watering-places has already been 
adverted to; but whilst the whole vegetation in purely pastoral 
districts is affected more or less by this trampling, yet the effect 
upon the growth of certain species of grasses is of a more particu- 
lar kind. Those whose seeds are provided with long awns, such 
as Andropogon, Aristida, Stipa, &ec., are able to penetrate the soil 
and await the rains to germinate them, while the more valuable 
and nutritious ones—as, for instance, Panicum, Sorghum, Sporo- 
bolus, &c.—being without those special arrangements, are liable 
to disappear, not alone from the difficulty of obtaining suitable 
lodgment in the ground, but also from all stock preferring their 
more succulent stems to the hard siliceous culms of their rivals. 
From these causes, overstocking, rabbits, and introduced 
plants, it appears probable that in the near future the features 
peculiar to the Australian landscape from its endemic floras will 
be greatly modified. As, for instance, the aspect of our Pacific 
slope has been in certain spots much altered by the spread of the 
cactus, and our water-courses are choked up in various parts of 
the colonies by the spread of the common water-cress (Nasturtium 
officinale). 
