576 MR, G. BENTHAM ON COMPOSIT X. 
Australia and Xanthiums in South Europe) in certain situations 
smother out the native vegetation. Xanthiwms, indeed, amongst 
annuals, and probably also Erigeron canadense, appear to possess 
this individual vitality to a very great degree. Xanthium struma- 
rium, a great nuisance in the southern vineyards, on account of 
the disagreeable flavour it is supposed to or actually does impart to 
the wine, however carefully hoed up will, if left on the soil, most 
readily take root again and grow. But perennials with creeping 
roots or underground rhizomes capable of sending up shoots 
from any small portion left in the soil enjoy and avail themselves 
of this vitality in the highest degree; and this, much more than 
the supposed efficiency of the pappus, appears to be the great 
cause of the extension of such plants as Tussilago farfara, Cnicus 
arvensis, Taraxacum dens-leonis, due. 
The introduction and establishment of colonizing plant-races 
is now proceeding so rapidly, especially in new countries such as 
Australia, New Zealand, central and western North America, &c., 
and the attention of local naturalists is so generally called to it, 
that we must expect numerous observations in correction of many 
of the foregoing conjectures, and in elucidation of the theories of 
the changes which are now taking place, and have from time 
immemorial taken place, in the vegetation and plant-distribution 
over the surface of our globe. 
Coxcrvusrox. 
If, after summing up the data collected in the foregoing pages, 
we attempt any general conclusions as to the special fatherland 
of Composite, their original birth-place, the history of their 
migrations, and their present homes of predilection, all that we 
can put forward as plausible conjecture is:—that Africa, West 
America, and possibly Australia possessed the order at the 
earliest recognizable stage, Africa showing the greatest variety 
of individual isolated remnants of extinct races, Andine America 
and some of the scattered islands showing a few of what may be 
deemed the nearest approach to what we have conjectured to have 
been the primitive form of the order; that at this early period 
there must have been some means of reciprocal interchange of 
races between these regions; that, since the disruption of this 
intercourse between the two great divisions of the globe, there 
must have been for a time acertain continuity of Composite races 
across the tropics from south to north, a continuity which was 
