464 Iy. EXPLANATIONS OF THE 
Highland counties, which certainly produce Caltha palustris also, 
the stated distribution in the Synopsis equally answers for the 
C. palustris, whether the C. radicans be included or be excluded. 
The same holds true of Ranunculus reptans and Geranium lan- 
castriense ; but here subject to some differences of opinion, as to 
whether these names should be applied strictly to very local 
plants, or more loosely to include other plants and localities also. 
Sarothamnus prostratus and Genista humifusa are very local 
varieties; and whether we unite them with the widely diffused 
Sarothamnus scoparius and Genista tinctoria, or separate them, 
the formulary distribution of these two latter remains unchanged. 
2. Aliens.—These follow close on the denizens of the Synopsis. 
They may be said to differ from the latter only by being under 
greater distrust of their claims to be accounted aboriginal natives 
of Britain. Some few of them are so perfectly established amid 
the native vegetation, that no question might have arisen against 
their nativity here, had it not been known that their wildness in 
Britain is recent, and that they came into the Old World from 
America within the dates of modern history. Such are Hlodea 
canadensis, so recently and so rapidly spread through England in 
damaging abundance; Impatiens fulva and Mimulus luteus, locally 
well established; LErigeron canadensis and Oxalis stricta, more 
casual and changeable in their places. 
Others, of unknown origin, have become so well established in 
many places that botanists are beginning to believe that they 
must have existed in this country from pre-historic times, having 
originally got into it through natural agencies alone, quite inde- 
pendently of human agency. If all or most of us had concurred in 
this view, of course the plants in question would have been treated 
as natives. If opinions and evidences had seemed to be about on 
an even balance, the plants would have come under the category 
of denizens. They are classed with the alieus because only a 
minority regard them in the higher predial character; while the 
majority among those botanists best prepared to give a verdict, 
through general experience and trained judgment, hold a contrary 
