222 NATURAL HISTORY. 



existed (since the differentiation of our existing species of 

 plants took place) a connection by continuous land 

 between Spain and Ireland, Forbes boldly faced the 

 problem. He brought forward geological and palaeonto- 

 logical evidence in support of the daring hypothesis that 

 towards the close of the Miocene period a great tract of 

 land, ' bearing the peculiar flora and fauna of the type now 

 known as Mediterranean, extended far into the Atlantic 

 past the Azores and that, in all probability, the great 

 semicircular belt of Gulf-weed ranging between the 

 fifteenth and forty-fifth degrees of north latitude, and 

 constant in its place, marks the position of that ancient 

 land, and had its parentage on its solid bounds.* Over 

 this land that flora, of which we have now a few fragments 

 in the west of Ireland, might with facility have migrated.' 

 On this hypothesis, the peculiar 'Asturian' plants of 

 Cornwall, Devonshire, and Western Ireland are the 

 remains of the oldest flora in the British Islands, and 

 their introduction into our area took place at the end of 

 the Miocene period. 



* Tfhe Gulf-weed (Sargassum bacciferum] is the seaweed which gives rise to the 

 ' Sargasso-sea ' so well known to navigators since the time of Columbus. Though 

 not now attached, it is very closely related to species of Sargassum which are 

 essentially littoral seaweeds, or live in shallow water near the shore. Eminent 

 botanical authorities, therefore, are of opinion that the Gulf- weed was at one time a 

 fixed seaweed, and that its present condition is an abnormal one. As the present 

 Gulf-weed does not propagate itself by fructification, but apparently simply by 

 breakage, this view would seem to be very probably correct. In this case there is 

 much to be said for the hypothesis of Forbes, that the present belt of Gulf-weed 

 in the Atlantic marks the position of an ancient coast-line, now deeply submerged. 



