To J. D. Hooker 23 February 
Down Bromley Kent
I hope you will excuse the freedom of my address, but I feel that as co-circum-wanderers & as fellow labourers (though myself a very weak one) we may throw aside some of the old-world formality.— Absence from home has prevented me sooner answering your note.1 If you send the earth &c &c by any public conveyance, wd you send it to “43 Grt. Marlborough St”,2 if otherwise either the Geolog. Soc. or Athenæum will do perfectly.— Of course you will put Lat: & Long: to the Antarctic mud or iceberg infusoria.— I have not yet heard from Ehrenberg.— I have just finished a little volume on the volcanic isld which we visited;3 I do not know how far you care for dry simple geology, but I hope you will let me send you a copy.— I suppose I can send it from London by common coach conveyance.—
I am quite ashamed of myself that I omitted to thank in words, but not in my mind, Sir. W. Hooker, for his kind invitation to myself to Mrs Darwin to visit the gardens at Kew;4 I fear it is not likely we shall be able, though it wd give us great pleasure.
I am going to ask you some more questions, though I daresay, without asking them, I shall see answers in your work, when published, which will be quite time enough for my purposes. First for the Galapagos, you will see in my Journal, that the Birds, though peculiar species, have a most obvious S. American aspect:5 I have just ascertained the same thing holds good with the sea-shells.—6 Is it so with those plants, which are peculiar to this archipelago; you state that their numerical proportions are continental (is not this a very curious fact?) but are they related in forms to S. America.— Do you know any other cases of an Archipelago, with the separate islands possessing distinct representative species? I have always intended, (but have not yet done so) to examine Webb & Bert: on the Canary Isd for this object.7 Talking with Mr Bentham,8 he told me that the separate islds of the Sandwich Arch: possessed distinct representative species of the same genera of Labiatæ: would not this be worth your enquiry? How is it with the Azores; to be sure the heavy West: gales wd tend to diffuse the same species over that group.—
I hope you will (I daresay my hope is quite superfluous) attend to this general kind of affinity in isolated islands; though I suppose it is more difficult to perceive this sort of relation in plants, than in birds or quadrupeds, the groups of which are, I fancy, rather more confined. Can St. Helena be classed, though remotely, either with Africa or S. America? From some facts, which I have collected, I have been led to conclude, that the Fauna of mountains are either remarkably similar (sometimes in the presence of the same species & at other times of same genera) or that they are remarkably dissimilar;9 and it has occurred to me, that possibly part of the peculiarity of the St. Helena & Galapagos Floras may be attributed to a great part of these two Floras, being mountain Floras.— I fear my notes will hardly serve to distinguish much of the habitats of the Galapagos plants, but they may in some cases;10 most if not all of the green, leafy plants come from the summits of the islands, & the thin, brown leafless plants come from the lower arid parts: would you be so kind as to bear this remark in mind, when examining my collection.
I will trouble you with only one other question. In discussion with Mr Gould,11 I found that in most of the genera of birds, which range over the whole or greater part of the world, the individual species have wider ranges: thus the Owl is mundane, & many of the species have very wide ranges.12 So I believe it is with land & fresh-water shells—& I might adduce other cases. Is it not so with crptogamic plants; have not most of the species wide ranges, in those genera which are mundane— I do not suppose that the converse holds viz—that when a species has a wide range, its genus also ranges wide:— Will you so far oblige me by occasionally thinking over this. It wd cost me vast trouble to get a list of mundane phanærogamic genera & then search how far the species of these genera are apt to range wide in their several countries; but you might occasionally in the course of your pursuits, just bear this in mind, though perhaps the point may long since have occurred to you or other Botanists.13 Geology is bringing to light interesting facts, concerning the ranges of shells; I think it is pretty well established, that according as the geographical range of a species is wide, so is its persistence or duration in time.—14
I hope you will try to grudge as little as you can the trouble of my letters, & pray believe me, very truly your’s, | C. Darwin
P.S. I should feel extremely obliged for your kind offer of the sketch of Humboldt; I venerate him, & after having had the pleasure of conversing with him in London,15 I shall still more like to have any portrait of him.—
Has just completed Volcanic islands.
Sends queries on Galapagos flora in particular and island floras in general; also on relationship of wide-ranging species to wide-ranging genera.
Please cite as
Darwin Correspondence Project, “Letter no. 736,” accessed on 18 January 2017, http://www.darwinproject.ac.uk/DCP-LETT-736