1 S 85 .] The Parasites of Civilisation. 393 
grease, and human excrement, as readily as plants, growing 
or decayed. The sparrow is omnivorous, though it greatly 
prefers grains, fruits, &c., to flies and larvae. The house- 
fly is the very type of an omnivorous animal. It consumes 
all the varied substances which enter into the diet of man, 
and a few more. Our most rampant weeds are proverbially 
hardy. With many nothing will kill them save individual 
extraction from the soil and consumption by fire. But, in a 
clayey soil, to remove every fragment of the root of a wild 
convolvulus is almost an impossibility. We have been told 
by a labourer who had been employed in laying the sewers 
of a country town that the roots of this weed were traced 
down to a depth of eleven feet. The tenacity of the dock, 
the thistle, the buttercup, the dandelion, and the groundsel 
is well known, and few indeed are the fields, or even the 
gardens, which are completely freed from these enemies. 
Perhaps we have here a consideration which may lead us 
to a definition — approximate at least — of vermin and weeds. 
There are, as we have already mentioned in passing, ani- 
mals, such as the wolf and the lion, which, though hostile 
to man, undergo extirpation wherever civilisation is tho- 
roughly established. Had France and Spain been for a 
couple of centuries occupied by the American people, it is 
safe to say that not a wolf would have survived down to 
this day. These animals, and many more that might be 
named, being extirpable and retreating before civilisation, 
cannot be called “ vermin.” In a similar manner there are 
many plants which we do not cherish and cultivate, and 
which have, indeed, nothing to recommend them, but 
against which we do not need to take any special precau- 
tions. Such plants, therefore, can scarcely be called 
“ weeds.” 
It is interesting to compare, when opportunity offers, a 
plot of land which has never, as far as is known, been sub- 
jected to cultivation, with another plot of similar soil which 
has once been cultivated, but has subsequently been left to 
what we may curiously call “ Nature.” Between the 
respective floras of these two plots there is a wonderful 
difference. The originally untilled plot contains an average 
assortment of the wild plants of the district. The plot 
which has been deserted will be found, as a rule, stocked 
exclusively with the most characteristic “weeds,” — vegetable 
species which seem to be fostered by cultivation, unless it is 
of the most thorough-going and persistent character. 
This brings us to another essential point : these parasites 
of civilisation, vermin and weeds, are notably ugly. Many 
VOL. VII. (THIRD SERIES) 2 E 
