To Asa Gray 8 June 
Down Farnborough Kent
My dear Sir
I thank you cordially for your remarkably kind letter of the 22d ulto , & for the extremely pleasant & obliging manner in which you have taken my rather troublesome questions. I can hardly tell you how much your list of Alpine plants has interested me, & I can now in some degree picture to myself the plants of your alpine summits. The new Edit. of your Manual is capital news for me: I know from your preface how pressed you are for room, but it would take no space to append (Eu.) in bracket to every European plant,1 & as far as I am concerned this would answer every purpose. From my own experience whilst making out English plants in our Manuals, it has often struck me, how much interest it would give if some notice of their range had been given, & so I cannot doubt your American enquirers, & beginners wd much like to know which of their plants were indigenous, & which European.
Would it not be well in the Alpine plants to append the very same additions which you have now sent me in M.S;2 though here, owing to your kindness, I do not speak selfishly, but merely pro bono Americano publico.—3 I presume it wd be too troublesome to give in your Manual the habitats of those plants found West of Rocky mountains; & likewise those found in Eastern Asia, taking the Yenesei (?)4 which, if I remember right according to Gmelin5 is the main partition line of Siberia. Perhaps Siberia more concerns the northern Flora of N. America. The ranges of the plants, to the East & West, viz whether most found are in Greenland & Western Europe, or in E. Asia appears to me a very interesting point as tending to show whether the migration has been Eastward or Westward.— Pray believe me, that I am most entirely conscious that the only use of these remarks is to show a Botanist what points a non-Botanist is curious to learn; for I think everyone who studies profoundly a subject often becomes unaware what points the ignorant require information. I am so very glad that you think of drawing up some notice on geographical distribution, for the area of the Manual6 strikes me as in some points better adapted for comparison with Europe than that of the whole of N. America.—
You ask me to state definitely some of the points on which I much wish for information; but I really hardly can, for they are so vague, & I rather wish to see what results will come out from comparisons, than have as yet defined objects. I presume that like other Botanists you would give for your area, the proportions (leaving out introduced plants) to the whole of the great leading families: this is one point, I had intended (& indeed have done roughly) to tabulate from your Book, but of course I could have done it only very imperfectly. I should, also, of course have ascertained the proportion to the whole Flora of the European plants (leaving out introduced) & of the separate great families, in order to speculate on means of transportal. By the way I ventured to send a few days ago a copy of the Gardeners’ Chronicle,7 with a short report by me of some trifling experiments which I have been trying on the power of seeds to withstand sea-water. I do not know, whether it has struck you, but it has me, that it would be adviseable for Botanists to give in whole numbers, as well as in the lowest fraction, the proportional numbers of the Families.— thus I make out from your Manual that of the indigenous plants the proportion of the Umbelliferæ are 361798=149; for without one knows the whole numbers, one cannot judge how really close the numbers of the plants of the same family are in two distant countries; but very likely you may think this superfluous.—8 mentioning these proportional numbers, I may give as an instance of the sort of points, & how vague & futile they often are which I attempt to work out, that reflecting on R. Brown & Hooker’s remark, that near identity of proportional number of the great Families, in two countries, shows probably that they were once continuously united,9 I thought I would calculate the proportions, of, for instance, the introduced Compositæ in Grt. Britain to all the introduced plants, & the result was 1092=19.2. In our aboriginal or indigenous flora the proportion is 1/10; & in many other cases I found an equally striking correspondence: I then took your Manual, & worked out the same question; here I found in the Compositæ an almost equally striking correspondence, viz 24206=18 in the introduced plants, and 2231798=18 in the indigenous; but when I came to the other Families, I found the proportions entirely different showing that the coincidences in the British Flora were probably accidental!—10
You will, I presume, give the proportion of the species to the genera, ie show on an average how many species each genus contains; though I have done this for myself.—
If it would not be too troublesome do you not think it wd be very interesting, & give a very good idea of your Flora, to divide the species into 3 groups, viz (a) species common to the old word, stating numbers common to Europe & Asia (b) indigenous species, but belonging to genera found in the old world, & (c) species belonging to genera confined to America or the New World. To make, (according to my ideas perfection perfect) one ought to be told whether there are other cases like Erica of genera common in Europe or in old world not found in your area.—
But honestly I feel that it is quite ridiculous my writing to you at such length on such subject, but as you have asked me, I do it gratefully, & write to you, just as I should to Hooker, who often laughs at me unmercifully, & I am sure you have better reason to do so.—
There is one point, on which I am most anxious for information; & I mention it with the greatest hesitation, & only in the full belief that you will believe me that I have not the folly & presumption to hope for a second that you will give it, without you can with very little trouble. The point can at present interest no one but myself, which makes the case wholly different from geographical Distribution. The only way in which, I think, you possibly could do it with little trouble, wd be to bear in mind, whilst correcting your Proof-Sheets of the Manual, my question, & put a cross or mark to the species, & whenever sending a parcel to Hooker to let me have such old sheets. But this wd give you the trouble of remembering my question, & I can hardly hope or expect that you will do it.— But I will just mention what I want, it is, to have marked the “close species” in a Flora, so as to compare in different Floras whether the same genera have “close species”, & for other purposes too vague to enumerate.— I have attempted by Hooker’s help to ascertain in a similar way whether the different species of same genera in distant quarters of the Globe are variable or present varieties. The definition I should give of a “close species” was one that you thought specifically distinct, but which you could conceive that some other good Botanist might think only a race or variety;—or again a species that you had trouble, though having opportunities of knowing it well, in discriminating from some other species. Supposing that you were inclined to be so very kind as to do this, & could (which I do not expect) spare the time, as I have said, a mere cross to each such species in any useless proof-sheets, would give me the information desired, which, I may add, I know must be vague.—
How can I apologise enough for all my presumption, & the extreme length of this letter? the great-goodnature of your letter to me, has been partly the cause, so that, as is too often the case in this world, you are punished for your good deeds.
With hearty thanks | Believe me | Your’s very truly & gratefully | Ch. Darwin
P.S. Thank you for answering my questions about the distance of the Alpine summits & about intervening lower land: I have no very good map, but I cannot make what you say tally at all, & suspect that you have written wrong figure. you say that the White Mts are separated from the Green mountains by 150 or 200 miles (geographical?) of intervening lower country; & the Green Mts from those of New York by about the same distance,—which wd make 300–400 miles— Perhaps at some future time, you would tell me how this can be.—11
Suggests AG append ranges to the species in the new edition of his Manual.
Is interested in comparing the flora of U. S. with that of Britain and wishes to know the proportions to the whole of the great leading families and the numbers of species within genera. Would welcome information on which species AG considers to be "close" in the U. S.
Please cite as
Darwin Correspondence Project, “Letter no. 1695,” accessed on 8 December 2016, http://www.darwinproject.ac.uk/DCP-LETT-1695