468 IV. EXPLANATIONS OF THE 
retrospective and prospective, the larger number of species no 
longer findable in recorded localities, may have more truly 
belonged to the list of errors, next to be mentioned. 
5. Errors.—Unfortunately these are rather numerous. At 
first thought, it might seem allowable and even more judicious to 
let them drop out of notice altogether. An objection arises 
against this course, in the difficulty of deciding which are certainly 
errors, and which are only uncertainly so; these latter of course 
linking the present category closely with the others. If a plant 
cannot be found now in a locality formerly reported for it, there 
is a more or less uncertain choice between declaring it a case of 
extinction or a case of misnomer, as before intimated. Even the 
preservation of specimens in herbaria is by no means always 
satisfactory evidence, to warrant a decision in favour of extinction 
as against error. If it were held so, we should be compelled to 
accept the American Potentilla tridentata as having been a 
‘genuine britisher’ up to a modern date, though found only by 
George Don. And the same with several other plants, alleged 
by Don to have been found wild in Scotland, and his specimens 
of which still exist in herbaria. In some cases, too, we seem to 
have better authority than Don, for the former finding of plants 
on the northern mountains, which have subsequently been 
sought there unsuccessfully. Examples of this occur in Veronica 
fruticulosa, alleged to have been found in Scotland by Robert 
Brown; and in Hieraciwm villosuin, alleged to have been picked 
there by Thomas Drummond. Considering the wild character of 
their reported habitats, and that wide spaces among the Highland 
mountains remain still almost unexamined, we are scarcely yet 
entitled absolutely to dismiss these plants unnoticed in any full 
enumeration of plants British and possibly British. That the list 
of Highland plants was not completed by our predecessors, has been 
made quite clear by the first finding or first recording of some 
of them in post-Donian times. Pseudathyrium alpestre, Sagina 
nivalis, Astragalus alpinus, and other indisputably native plants 
are among such recent additions to the Scottish flora. 
