54 INVOLUTION [Chap. II 



Letter 20 account for the little group of Asturian plants — few as to 

 species, but playing a conspicuous part in the vegetation — 

 giving a peculiar botanical character to the south of Ireland ; 

 that, as I had produced evidence of the other floras of our 

 islands, i.e. the Germanic, the Cretaceous, and the Devonian 

 (these tdrms used topographically, not geologically) having 

 been acquired by migration over continuous land (the glacial 

 or alpine flora I except for the present — as ice-carriage might 

 have played a great part in its introduction) — I considered it 

 most probable, and maintained, that the introduction of that 

 Irish flura was also effected by the same means. I held also 

 that the character of this flora was more southern and more 

 ancient than that of any of the others, and that its fragmentary 

 and limited state was probably due to the plants composing it 

 having (from their comparative hardiness — heaths, saxifrages, 

 etc.) survived the destroying influence of the glacial epoch. 



My geological argument now is as follows : half the 

 Mediterranean islands, or more, are partly— in some cases (as 

 Malta) wholly — composed of the upheaved bed of the Miocene 

 sea ; so is a great part of the south of France from Bordeaux 

 to Montpellier ; so is the west of Portugal ; and we find the 

 corresponding beds with the same fossils (Pecten latissimus, 

 etc.) in the Azores. So general an upheaval seems to me to 

 indicate the former existence of a great post-Miocene land [in] 

 the region of what is usually called the Mediterranean flora. 

 (Everywhere these Miocene islands, etc., bear a flora of true 

 type.) If this land existed, it did not extend to America, for 

 the fossils of the Miocene of America are representative and 

 not identical. Where, then, was the edge or coast-line of it, 

 Atlantic- wards ? Look at the form and constancy of the great 

 fucus-bank, and consider that it is a Sargassum bank, and that 

 the Sargassum there is in an abnormal condition, and that 

 the species of this genus of fuci are essentially ground-growers, 

 and then see the probability of this bank having originated 

 on a line of ancient coast. 



Now, having thus argued independently, first on my 

 flora and second on the geological evidences of land in the 

 quarter required, I put the two together to bear up my Irish 

 case. 



I cannot admit the Sargassum case to be parallel with that 

 of Confervas or Oscillatoria. 



