III. INTRODUCED SPECIES. 67 



out the aiding interference of mankind, introduced spe- 

 cies are then deemed > naturalised. It is much to be 

 regretted that an excessive laxity has prevailed among 

 British botanists in their use of this term. Several of 

 them apply it to mere casual stragglers which have 

 acquired no constant or permanent localities ; some of 

 them even to trees and long enduring herbs, which sim- 

 ply continue to live and grow where planted ; and which 

 thus increase only in their dimensions, not by numbers. 

 Strictly, no species ought to be deemed naturalised un- 

 less it maintains its ground here by seeds or other usual 

 mode of multiplication, and unaided by human agency. 



M. Alphonse De Caudolle would limit the use and sig- 

 nification of the term so strictly as to exclude even those 

 agrestal species, such as the poppies and fumitories, 

 which appear to be in anywise dependant upon agricultu- 

 ral operations for rendering the soil suitable to their sup- 

 port. Though this may be considered the just and 

 philosophic view, scarcely any British botanist has ap- 

 proximated to such a degree of strictness. In some mea- 

 sure it was attempted in the definitions in the first 

 volume of the present work, page 63, by separating the 

 colonists from the native species, and placing them below 

 the doubted category of denizens, — below those species 

 which may possibly be natives, may possibly be aliens. 

 It was thus tacitly assumed that most of the annual 

 weeds of corn fields and other cultivated ground, seldom 

 found elsewhere, had been originally imported into this 

 island, howsoever abundant and widely diffused they may 

 have since become. But in general British botanists 

 place those weeds in the category of undoubted natives. 



M. De Candolle has further suggested, that there 

 ought to have been in this work a special category for 

 naturalised species, in contradistinction against those for 



