INTKODUCTION. 



liii 



Number of species and 

 Orders in Ireland, 

 centage ratios to th 



sub-species in each of the prevalent Natural 

 in England, and in Europe, with their per- 

 i total floras. 



Numbers and percentages. 



Diversities of opinion as to tte limits of species must always 

 introduce an element of uncertainty into estimates such, as ttat 

 given in the foregoing table ; but in the present instance the autho- 

 rities made use of are not so -widely at variance in their views on 

 this point as to make the results to any serious degree untrust- 

 worthy. In the case of the order Composite, however, the process 

 of segregation in the genus Hieracium has been carried so much 

 farther by Continental botanists than by Hooker, our species standard 

 for England and Ireland, that the percentage ratio of that order for 

 Europe is no doubt overstated, perhaps by so much as one per cent. 



VI. Plants enbemic in Ieeiand. 



The endeavour to establish the existence of peculiar plant-forms 

 in Ireland is of great interest in connection with the theory of 

 organic evolution. A few Irish plants have been proposed as truly 

 endemic, or peculiar to the island, but they are all of them more or 



e 



