352 



IProo. B.N.F.C., 



parts and if a plant is found in one and not in the other— the 

 reason for its absence should be determined if possible. Buffon 

 said that at certain temperatures one should get similar floras and 

 faunas but similar climates did not produce similar floras in all 

 respects, therefore a group of species or a species might be 

 limited by natural barriers, e.g. the Field Daisy was absent from 

 America and the Hyacinth from Germany. 



The various obstacles which hindered distribution were then 

 dealt with in turn, beginning with human agency. This had 

 been so potent that many species were only left on cliff faces and 

 bogs. Aliens had been introduced and in some cases had spread 

 very rapidly, but in time the majority of them died out. The 

 Ivy-leaved Toad-flax had been able to hold its own on old walls 

 and the Sweet Flag, Acorus Calamus, was abundant in the Lagan 

 Canal. Again Andromedq polijolia, which grows in a bog near 

 Donaghadee with Calluna and the Bog Myrtle, was disappearing ; 

 the reason being that it grows with a fungus which is absolutely 

 necessary for its welfare — if the fungus was absent it could not 

 flourish as it had no root hairs and so could not obtain the 

 mineral salts necessary for healthy growth. 



Another obstacle to the world-wide distribution of plants 

 was climate. Each and every plant corresponded to every factor 

 which went to make up the climate. A certain amount of light, 

 warmth and moisture was necessary or the plant would die even 

 if other conditions were suitable. 



By means of distribution maps Mr. Bennett showed that 

 certain plants occurred in Co. Down and not in Antrim, while the 

 reverse also held good. It was further seen that some plants 

 were confined to particular river basins. The case of Dry as 

 octopetela was instanced as one whose distribution depended on 

 climatic factors, it being found on Snowdon, in the Scottish 

 Highlands, the Lake District, and mountain stations in Donegal, 

 Derry and Antrim. Also the dwarf Mountain Willow — Salix 

 kerbacea. The third obstacle to distribution was the nature of 



