SUGGESTIONS TOWARDS A SOLUTION OF THE 



PROBLEM OF THE IBERIAN PLANTS IN 



SOUTH-WEST IRELAND. 



By G. W. BULMAN, M.A., B.Sc. 



We do not propose to give here any review of the 

 subject, or to criticise any of the explanations which 

 have been brought forward. On the assumption 

 that a land connection between Spain and Ireland 

 was necessary, and that such really existed, we offer 

 a suggestion as to why these Irish species do not also 

 occur in England. None of the theories we have 

 come across explain this, or even admit it as a 

 difficulty. 



Again, assuming that the land connection was 

 pre-Glacial, and that there has been none since the 

 retreat of the ice, we will enquire what grounds 

 there are for believing that much of our present flora 

 may have survived glaciation. 



As regards the first point, it is practically 

 impossible to imagine a land connection between 

 Spain and Ireland which did not also include 

 England. And it is to be remembered that Cornwall 

 also has its own peculiar species of Southern plants, 

 which equally need a land connection. The Spanish 

 plants spreading across the assumed land bridge 

 would have had time to reach England also. Why 

 are they, then, not found in this country ? One is 

 inclined to suggest at first — and the suggestion has 

 indeed been made — that they were driven out by the 

 cold of the Glacial epoch everywhere but in the south- 

 west of Ireland. To this, however, it may be replied 

 that if they could survive there they could surely 

 do so also in Cornwall and the Scilly Islands. We 

 propose, then, another explanation, founded on the 

 influence of the geological structure of the land on 

 the spread of plants. Let us suppose a set of plants 

 spreading northwards along a line sufficiently 

 extended to reach along our south coast to some 

 distance west of the extreme south-west corner of 

 Ireland. Normally such a migrating band of plants 

 would reach England and Ireland simultaneously. 

 But let us suppose that the advancing front of the 

 Iberian plants meets with a wedge-like barrier of 

 unsuitable ground, mountains, desert, marsh, on 

 merely a different sort of rock. The advance is 

 thereby turned to the north-west and north-east or 

 the two sides of the barrier. The former branch in 

 due course reaches the south-west of Ireland, and 

 the then existing land to the west of this. The 

 other diverges so far that by the time it reaches our 

 latitudes it is too far east to touch our shores. Or 

 the nature of the barrier may have been such as to 

 stop the species altogether from getting further 

 north. The present continental distribution of the 



species in question, if known in sufficient detail, 

 might possibly indicate which way it was. But the 

 barriers of unsuitable country which prevented the 

 Irish species reaching England may have favoured 

 the spreads of the southern species now found in 

 Cornwall, and the migrating area of the Cornish 

 species may have tapered northwards, and had its • 

 apex in Cornwall, which would account for their 

 absence in the eastern part of southern England. 



As regards our second point, a careful considera- 

 tion of the facts seems to suggest the possibility — if 

 not the strong probability — of the survival of many, 

 at least, of our native plants over the Glacial epoch. 

 That the whole of our flora and fauna was driven out 

 or exterminated by the cold is, perhaps, only held by 

 those who have had the " Glacial nightmare " badly. 

 Yet even those who take more moderate views 

 might be excused for doubting the possibility of a 

 fragment of the Spanish flora surviving glaciation 

 in the south-west of Ireland. Let us ask, then, 

 What evidence can be brought forward indicating the 

 possibilities of survival ? The present flora of Green- 

 land seems to furnish a strong argument. In spite 

 of its glaciation this country possesses at the present 

 day a considerable number of species of flowering 

 plants. Some of these are members of our own 

 flora. Even, then, if we suppose the glaciation of 

 our land was as severe as that of Greenland to-day, 

 we have here absolute proof that some of our species 

 could survive. But it is not probable, in fact, it 

 seems impossible, that the climate of Glacial Britain 

 was as severe as that of Greenland to-day. Even if 

 the amount of ice and snow was as great, or greater, 

 Britain would still have the advantage of its more 

 southern latitude. The amount of heat received 

 during the summer would be as great as — or, 

 according to some authorities, greater than — at 

 present. The amount of land freed from ice 

 and snow during this season would be greater, and 

 the time it remained free longer. Thus, there would 

 be a greater possibility of survival than in Greenland 

 to-day. But this is not all. It is difficult to under- 

 stand how Greenland can have received its present 

 flora since the Glacial period. The ordinary means 

 of transport, winds, ocean currents, and so on, are not 

 available for Greenland ; nor is there any suitable 

 land connection ; and Greenland's migratory birds 

 go to it in the spring when there are no ripe seeds 

 for them to carry. It almost seems as if we would 

 have to grant that Greenland's present flora survived 



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