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In North-Western Victoria and South Australia, where very 
extensive tracts have been cultivated in the ‘mallee scrubs,” it 
might have been expected that the original mallee (Zucalyptus 
oleosa and E. gracilis) would have reappeared, but so far this is 
not the case, as wherever that mode of cultivation known as 
“mullenizing” has been sufficiently prolonged to ensure the death 
of the primitive growth by uprooting the underground stem— 
popularly known as the “mallee root”—regeneration is almost 
wholly unknown, and if thoroughly stocked with sheep, it never 
does take place, owing to the infrequent germination of the seeds 
and the extreme slowness of growth of the seedlings. 
Sufficient time has not yet elapsed since settlement took place 
to formulate the conditions under which the original vegetation 
can be expected to reclothe the surface exhausted by farming, 
but in the cooler and moister regions we find, as stated above, 
that Hucalyptus rostrata does rapidly resume its sway over the 
cultivated tracts where it originally prevailed; but in the warmer 
and drier zones we are without any extensive examples of the 
native vegetation reasserting its dominion. These former areas 
present the best examples of the overwhelming growth of intro- 
duced weeds—the stinkwort (Inula graveolens) in summer, and 
the Cape weed (Cryptostemma calendulacea) and sundry thistles, 
&c., Im spring. In the tropical region, however, where abandoned 
sugar-cane fields are now covered with Lantana, we may expect 
the original dense growth to reappear by degrees. 
Necessarily as cultivation proceeds a larger area becomes 
despoiled of all the native plants. the forests are cleared, and 
repeated ploughings complete the extermination. Here, intro- 
duced plants find a suitable habitat for propagation, and each 
isolated farm becomes a centre of dissemination of the various 
weeds, which injuriously affect the grain-crops in the northern 
hemisphere ; a list of these troublesome plants would be very 
extensive, and it is steadily increasing, and although some few 
annuals of indigenous growth reproduce in these cultivated 
spots, yet none of them do so to any injurious extent, none can 
therefore be considered ‘“ weeds.” 
It would be very ditticult to indicate any Australian plant 
which has increased in numbers while the land is regularly culti- 
vated for a lengthened period; intermittent cultivation does, 
however, tend to the individual-increase of certain vigorous 
species, thus on limestone soils we find Zygophyllum, Hrodiwm, 
Erysimum, &c., similarly where cultivation has been attempted in, 
or at the boundary of, the saltbush-country, which has prepared the 
soil for the retention of the seeds, and if stock be kept off for 
two or three years, the more tenacious plants, such as Kochza, 
Atriplex, &e., reappear. 
