1G2 
And now, for a few minutes, may I ask your attention to a 
subject of considerable interest and importance, which has occupied 
the attention of dsfoturalists in America more tlian it lias done on 
this side the Atlantic— I mean on the Migration of Plants, 
especially troni Europe to America. In the first place, I would 
ask, why is it that whilst we find an immense emigration to tlie 
West, Ave have but few instances of plants becoming established by 
immigration ?— one or two marked examples excepted, which I Avill 
briefly allude to. Eirst, in general and most rapid spread, we have 
the Anachans, or Elsdea canadensis, which, in a A^ery fcAV years, 
has overrun our ditches, rivers, and broads, at one time seriously 
threatening to impede the navigation in many districts ; but I do 
not antidpate that it will be long-lived amongst us, as I have 
noticed in several places that it has already died out. It Avas first 
noted in this country about the year 1847 , in the northern and 
midland counties, and in the south of Scotland ; how it became 
introduced is not knoAvn. 
The ballast hills in the Ilorth of England furnish a considerable 
number of Canadian and JSforth American species, but these only 
exist awhile, as it were, by sufferance ; and as far as I have beeii 
able to notice, no single plant has been established permanently by 
the means of ballast, which, a few years since, Avas very largely 
deposited on the sea banks of several of our northern rivers 
especially those of the Tyne and Wear. We might suppose that 
these would produce abundant and valuable additions to our 
flora ; but, as I have before said, something is against the intro- 
duction of tliem. Must it be that the old country, so to speak, 
has been Avorn out, and has quite enough to do to support its oAvn, 
let alone any iieAv-eomers. Did time permit, we should find the 
same AA'ould apjAly to the introduction of animals. 
Ckiytoma perfoliata, a North American species, has caused me 
some little difficulty, as it has sprung up, as it Avere perse, in remote 
and inland places. I have found it very plentifully, thirty years 
ago, near Ampthill, Eedfordshire, near a large sand-pit ; near the 
Newmarket Eoad, Norwich;"' also in the 'Workhouse Lane, Norwich ;'"' 
* I find tliat it Avas intentionally introduced in both these localitie.s. 
