74 III. INTRODUCED SPECIES. 



to place the several scores of other species, which he sees 

 to be intermediate between these two clear and extreme 

 examples. The colonists and also the denizens come be- 

 tween ; — species about which we cannot agree, whether to 

 accept them as natives, or to reject them as aliens origi- 

 nally ; — species which either now appear to require human 

 operations to fit the ground for their present continuance 

 in Britain, or still appear to have required such aid for 

 their original introduction and establishment, though no 

 longer needing that aid now to retain them here. — This 

 second class, the denizens, are best exemplified among 

 the garden plants ; the first or colonists, by the corn-field 

 plants. 



3. Ornamental garden plants. — These are liable to be 

 left growing in the sites of old gardens, which have ceased 

 to be cultivated ; and in the lapse of time, after vestiges 

 of adjacent buildings have become indistinct, the plants 

 are mistaken for native productions, by recent observers 

 to whom the former condition of the ground remains un- 

 known. From such sites, and also from gardens still 

 under care, various species may and do spread away by 

 seeds and runners, or by other modes of increase and dif- 

 fusion. When thrown out as superfluities among refuse 

 from gardens, many roots and capsules of seeds are con- 

 veyed to the fields and road sides, or are carried by 

 streams to other situations comparatively remote ; where 

 they grow, and thus gradually become established. Oc- 

 casionally plants are introduced by design to wild-seeming 

 localities, either with experimental views, or (by guides 

 and dealers) for the purpose of fraud and deception. As 

 a general rule, we may suspect ordinary garden species to 

 have been originally escapes or introductions, if found 

 seemingly wild in only few and isolated places ; and these 

 being spots which either suggest their garden origin, or 



