1909. Adams. — Distinguishing Plants in Ireland, 123 



ON THE POSSIBILITY OF DISTINGUISHING 



BETWEEN NATIVE AND AUEN SPECIES 



OF PLANTS IN IRELAND. 



BY J. ADAMS, M.A. 



[Read before the Dublin Naturalists' Field Club, 9 February, 1909.] 



The flora of a countr)^ such as Ireland is slowly but steadily 



changing. As the result of the destruction of most of the 



ancient forests, followed by agricultural and trading operations, 



many of the aboriginal species have been compelled to narrow 



their limits, or have even vanished altogether from districts 



where the}^ formerlj^ abounded. At the same time other 



species have extended their range, being more at home on the 



artificial medium thus created ; while to complicate matters 



still further, foreign species have been introduced, some of 



which appear to be as much at home in our climate as the 



real Hibernian species themselves. It will be evident to the 



student of the geographical distribution of plants that correct 



ideas on the origin and afiinities of the Irish flora can onlj^ 



be arrived at b}^ taking into consideration the species that are 



native to the country, and leaving out of account those that are 



known to have been introduced. Considerable difference of 



opinion has existed among botanists of high rank, such as 



De CandoUe, Hooker and Arnott, Babington, and Watson, as 



to the exact standing of certain species, some considering 



them as genuine natives, others regarding them as introduced 



species. The following passage from Watson's " Compendium 



of the Cybele BritanniccC' seems well worthy of repetition in 



this connection : — 



" Inexperienced observers more readily believe in the true nativity of 

 plants ; while those of greater experience will frequently find grounds 

 for doubt or distrust: Besides this personal difference, the desire of 

 appearing as discoverers too often leads vain-glorious collectors to make 

 out the best case they can in support of the 'native claims ' of species 

 and the ' truly wild ' character of their localities." 



Watson divided British plants into five groups : — Natives, 

 Denizens, Colonists, Aliens, and Casuals. The last four 

 groups represented introduced species, and were arranged in 

 descending order according to their success in maintaining 

 a foothold in competition with the truly aboriginal species. 



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