PLAN OF THE FLORA. lx\i 



botanists have accepted the principles set forth in Watson's 

 " Cybele Britannica " and the "Compendium." their local 

 application is sometimes more a matter of conjecture than of 

 certainty.' " The terms, Native, Denizen, Colonist, Alien and 

 Casual, serve to express a descending series, from the truly 

 wild and pre-historically established species, down to the 

 occasional stragglers from cultivation, or the products of seeds 

 accidentally imported with merchandise, ship-ballast, or other- 

 wise." Mr. Watson proceeds to define these terms as fol- 

 lows : — 



(a) Native — "Apparently an aboriginal British species." 



(b) Denizen — "At present maintaining its habitats as if a 

 native species, without the direct aid of man, but liable to some 

 suspicion of having been originally introduced by human 

 agency, whether by design or accident." 



it) Colonist — "A weed of cultivated land, by road sides, 

 or about houses, and seldom found except in places where the 

 ground has been adapted for its production and continuance by 

 the operations of man ; with a tendency in some of them to 

 appear on the shores, landslips, and in what are called ' waste 

 places.' " 



(d) Alien — " Presumably introduced by human agency." 



(e) Casual — "Chance stragglers from cultivation; those 

 occasionally imported and sown with agricultural seeds ; those 

 introduced among wool, oil-seeds, or other merchandise; foreign 

 plants found on ballast heaps deposited from ships ; and gener- 

 ally such alien species as are most uncertain in place and 

 persistence." 



These definitions have been strictly adhered to, though the 

 application of them may be faulty at times. In practice the 

 classes shade off into one another ; e.g., some species may be 

 regarded either as denizens or aliens ; others either as colonists 

 or casuals ; again, the term alien or casual may often be used 

 indifferently. The rank assigned to any species here has, of 

 course, exclusive reference to its existence in the parish of 

 Halifax. Necessarily it cannot have a higher rank than in 

 Britain as a whole, so Watson's decision must be accepted as 

 an upward limit ; but it may have a lower rank, and in fact 

 cases frequently occur where species truly native elsewhere in 

 Britain are not native, but only denizens, casuals, etc., in this 

 district. Occasionally the addition of a note of interrogation 

 or an alternative denotes uncertainty at the time of compiling 

 the list. Longer experience would now lead me, in almost 



