Dear Darwin

Is there an evidence that the South of England & of Ireland, were not submerged during the Glacial Epoch, when the W. & N. of England were Islands in a glacial sea? And supposing they were above water, could the present Atlantic & N.W. of France Floras we now find there, have been there during the Glacial Epoch?— yet this is what Forbes demands, p 346. At p 347 he sees this objection & wriggles out of his difficulty by putting the date of the Channell “towards the close of the Glacial Epoch”¹

What does Austin make the date of the Channell—ante or post glacial?²

Origin Ed III. top of p. 344, how can the breaking of an isthmus give rise to an irruption of new inhabitants?³

I think you are wrong in Origin in implying that the true character of Insular Flora is altogether (or almost) due to herbaceous forms of nearest continent becoming arboreous: though the latter is a strong element too. N. Zealand is a heavy case to the contrary.⁴ Is DeCandolle right in saying Trees have restricted ranges?⁵ it is quite the contrary with Pines, Oaks, Beeches, Birches

Thanks for yours just received, which I should like to discuss with you—⁶ I had before your main arguments, quite clear, but you now send me some important developements.

You must not suppose me to be a champion of Continental Connection, because I am not agreeable to transoceanic migration.⁷ I have no fixed opinion on the subject—& am much in the state regarding this point, that the Vestiges left me in regarding species.⁸ What we want is, not new facts, but new ideas analogous to yours of Natural selection in its application to origin— Either hypothesis appears to me well to cover the facts of oceanic Floras, but there are grave objections to both, Botanical to your’s, Geological to Forbes.⁹

I intend to discuss the point with as little prejudice as I can at Cambridge¹⁰—in fact to d—d both hypotheses, or if you like to d—n Ed. Forbes & double d—n yours! for I suppose that is how you will take my fair play. I own that it is most disgusting to have no side, & I cannot tell you how it dispirits me with the whole thing. I shall make up for it by blessing Nat. selection & Variation—& they shall be blest—as necessary to either hypothesis, & therefore proving them to be twice as right as if it only fitted one!¹¹

By saying mountains south of Pyrenees I spoke foolishly. & should have said of North shore of Mediterranean.¹² Boissier gives a capital list—. of Grenadan alpines common to North.—¹³ I forgot all about S. Spain having mountains— I referred to Appenines, M^ts of Sardinia & of Atlas, in which I think no alpine plants occur, I think.

The absence of any alpine or subalpine plant of Spain in Madeira or Canaries puzzles me greatly, as they must have been Islands in your glacial sea (there is a sneer for you) & yet you must expect it from there being no boulders.¹⁴

?Have you anywhere stated that you regard the old elements of Madeira flora as remains of Tertiary epoch?¹⁵

I quite grant that the oldest forms have best chance of being developed into Trees.

I should like to look for old moraines on Pico. Erica Daboeci, a native of W. Ireland & Asturias, being common in two Islands, & Calluna on 3 are staggering facts.¹⁶

With regard to the specific differences between Porto Santo & Madeira, it seems pretty much most marked in shells,¹⁷ & they do seem to change very fast under some circumstances. Of course I should include them in the same continent: & should have thought its peculiarities quite as good evidence of the sunk continent theory as of the reverse— Two adjacent lands sink, gradually, till all that remains of one is a barren sunburnt rock, of the other a lofty moist wooded mountain. I should expect the organisms common to both, to be most changed by the struggle in the smaller & drier area.

The Azorean Flora is almost identical with the Madeiran, It has about 30 endemic species & varieties, which with 25 Maccronesian species,¹⁸ make 55 sp. out of about 350 difft. from Europe— Though upwards of 500 miles N. of Madeira & with M^ts. 7000 ft high, it contains only 3 plants of more boreal character than Madeira, viz. Viola palustris & Calluna vulgaris, both which however reached Grenada, & Littorella lacustris, a more boreal water plant which may have brought to the Lake by Gulls’ feet— Considering how much nearer these Islands are to Newfoundland on one hand & Britain on the other, this absence of more plants of either country seems marvellous.¹⁹ It also appears strange to me that Madeira should have contributed 25 of her otherwise endemic forms to such a distance & that they should have kept their characters.

The Islands want better exploring however.

Of course you know that the sea currents all set from the Atlantic Islands to the Mediterranean,—but that is a trifle to a sound migrationist!²⁰

We have not Duvernoya.²¹

Acropera will be sent tomorrow to be left at Bromley station.²²

Ever yr aff | J D Hooker