FLORA OF THE SCILLY ISLES. 105 
a continuation of the Cornwall and Devonshire range. It frequently 
lies ‘close to. the surface, but Mr. Statham* gives the following variety 
and. order of strata, which he states to be very general throughout the 
islands :— 
»1.- Black surface-soil with sand. 
2. Fine ash-coloured sand, containing fragments of shells. 
».8..-Reddish and chocolate clay, with angular granite blocks. 
4. Decomposed granite rubble, with larger granite masses. 
5. Granite roc 
These beds vey considerably in thickness in different localities. He 
thinks the occurrence of sand on the highest elevations a proof of fre- 
quent submergence, but he does not specify, or give any particulars 
respecting, the shells which he found in it. The recent deposits deserve 
the most careful examination, because of the important bearing oy 
have on the age of our southern flora. 
On comparing this insular flora with that of the mainland, it is evi- 
dent that both are derived from the same source by migration and not 
by transport... All the species hitherto met with in the Scilly Isles oc- 
cur also on the nearest mainland, except Arthrolodinm ebracteatum, a 
native of the Channel Islands and of France. Taking the law of 
migration from specific centres as granted, the plants of the French 
type have spread into these islands and the mainland, from the south or 
south-east, and in both cases the spreading must have taken place 
the existence of a vast continent, now partly occupied by the 
sea, which flowed in as a barrier before the 4rthrolobium spread fur- 
ther than the Scilly Isles. 
It is.true there seems hardly sufficient evidence to prove that any 
of the land south and south-west of the Thames was submerged during 
the glacial period ;+ but even if no such submergence took place, it is 
scarcely possible that the southern flora could have survived the glacial 
; it is much more probable that the extreme rigour of the climate 
destroyed it, and that it gave place to one of more arctic type ;f in 
* “ Geology of f Scilly Isles," read before the British Association, Sept. 
iby Rey. F.F. Statham, F.G.S. 
I The Antiquity z Man; by. Sir Charles Lyell; also a Eu by J. 
er, er, who held a opinion, Proe. Geol. aet qe 
= gin of Species, by Charles ‘Darwin, chapt ** Geographical ial Distri- 
—— ete. pisei cm Austen's paper on the valley of. the English Channel 
(Quar. Journ. Geo. Soc., vol. vi.) ; he is disposed to our characteristic south 
of: England f. flora to be of pliocene origin. 
