The Scottish Naturalist. 



235 



would be nc real difficulty in procuring the requisite assistance. 

 It would also add much to the value of the reports were the 

 names of the correspondents given once at least in full, to 

 authenticate the information supplied by them. 



As to the advisability of recording the disappearance of recent 

 introductions, casuals, escapes, &c, we are of opinion that it is 

 of real value to note the occurrence of such plants (duly indicated 

 as to their true nature in any locality), as affording a means of 

 tracing the progress and rate of naturalisation in certain localities 

 of certain species ; and the disappearance of such plants is also 

 worth a record, as tending to elucidate the conditions that 

 regulate the " survival of the fittest," or, in other words, the 

 reasons why certain forms become dominant and others succumb 

 in the struggle. But whatever the views entertained on this 

 point, there can be no question that, so far as possible, the various 

 species of such plants should receive uniform treatment, and this 

 is scarcely granted to them in the report ; certain species being 

 admitted into it though confessedly "abnormal," or "not native" 

 in the localities from which they are reported to have dis- 

 appeared; while others, with probably an equal claim to be 

 mentioned, have been excluded. 



Again, with regard to undoubtedly native species, not a few 

 have been mentioned as " extinct," on evidence that cannot be 

 regarded as in any way satisfactory, since it would be scarcely 

 possible to extirpate them, except by a change in their environ- 

 ments so great as to be most unlikely to occur over a moderately 

 wide area. In such cases it is most improbable that a careful 

 search would fail to prove the continued existence of the species 

 in their old localities, i.e. assuming that the earlier records were 

 based on correct identification, which may in a few cases be 

 reasonably doubted. Among such reported extirpations are most 

 of those reported for "Mid-Aberdeen;" for it can scarcely be 

 supposed that the following plants can have become wholly 

 extinct in that district, viz. : — Trollius europceus, L. ; Lotus pilosus, 

 Beeke; Droscra angtica, Huds. (also reported as "extinct in 

 Kincardine," in which county it is in truth common, though 

 local) ; Hippuris vulgaris L. ; Utricularia vulgaris L., and U. 

 minor L. ; three species of Spargam'um ; and Equisetum hyemale 

 L. ; and the same probably holds good of Botrychium Liuiaria 

 L., on the Pentiand Hills. The causes assigned for the disappear- 



