30 Origin of the British Flora. 



over six feet high. A few Rock Doves bred near the 

 place, and he concluded that an acorn had been brought by 

 one of these birds, but where from ? Unless it had been 

 picked up on the sea-shore, it must have been carried a 

 long way indeed. It could hardly have been brought by 

 man, as the place was very remote, as well as difficult of 

 access. Rooks occasionally cross the Pentland Firth. 

 The distance of the north of Hoy from the nearest point 

 where Oaks grow is fully as great as is the distance across 

 the Strait of Dover ; it is probably more than twice as 

 great as was the gap between England and France at the 

 period when the Oak was re-introduced after the Glacial 

 Epoch. Not only have the cliffs of Dover and of Calais 

 steadily receded through the inroads of the sea, but when 

 the ' submerged forests ' flourished both the English and 

 the French Coasts seem to have been bordered by a wide 

 belt of flat land covered with Oaks, the stumps of which are 

 now found rooted in the ancient soil as much as forty feet 

 below the present sea-level. 



The transportation of large edible seeds for such long 

 distances uninjured is probably of exceptional occurrence, 

 and is more probably due to rare accidents than to special 

 adaptation. Some years ago I found, for instance, in an 

 old chalk-pit the remains of a wood-pigeon which had met 

 with some accident. Its crop was full of broad-beans, all 

 of which were growing well, though under ordinary circum- 

 stances they would have been digested and destroyed. 

 As fully half at least of the birds that are hatched must 

 die by various accidents before the following season, it is 

 evident that this dispersal of the contents of their crops 

 must be of daily occurrence. A pigeon would easily cross 

 the Strait of Dover in half-an-hour, and in the days when 

 raptorial birds and wild cats were plentiful, many must 

 have been struck down with their last meal undigested. 



