From Asa Gray 16 February 1857
Feb. 16th, 1857
My Dear Mr. Darwin
I meant to have replied to your interesting letter of the 1st. Jany. long before this time, and also that of Nov. 24, which I doubt if I have ever acknowledged.— But after getting my School-book or Lessons in Botany off my hands1 —it taking up time far beyond what its size would seem to warrant—I had to fall hard at work upon a collection of small size from Japan—mostly N. Japan,—which I am only just done with.2 As I expected the number of species common to N. America is considerably increased in this collection, as also the number of closely representative species in the two, and a pretty considerable number of European species too.— I have packed off my mss. (tho’ I hardly know what will become of it) or I would refer you to some illustrations.3 The greater part of the identical species (of Japan & N. Amer.) are of those extending to or belonging to N.W. Coast of America; but there are several peculiar to Japan & E. U. States, E.g. our Viburnum lantanoides is one of Thunberg’s species.4 De Candolle’s remarkable case of Phryma, which he so dwells upon,—turns out, as Dr. Hooker said it would, to be only one out of a great many cases of the same sort.5 (Hooker brought Monotropa uniflora, you know from the Himalaya’s; and now, by the way, I have it from almost as far south, i.e. from St. Fé de Bogota, New Granada).—
There is another Japanese collection I shall have a chance to look over, presently, that made by Charles Wright.6 When that comes to be studied, it will be worth while to compare the Japanese & N. American Floras rather critically.7
Your anecdote of Agassiz, “Nature never lies” is most characteristic.8 Instead of learning caution from experience A. goes on faster than ever, in drawing positive conclusions from imperfect or conjectural data, confident that he reads Nature through and through, and without the least apparent misgiving that anything will turn up that he cannot explain away.
—Well, I never meant to draw any conclusions at all, and am very sorry, that the only one I was beguiled into should “rile” you, as you say it does:—that on p. 73 of my 2d. article: for if it troubles you it is not likely to be sound.9 Of course I had no idea of laying any great stress upon the fact (at first view so unexpected to me) that one third of our Alpine species common to Europe do not reach the arctic circle; but the remark which I put down was an off hand inference from what you geologists seem to have settled, viz. that the northern regions must have been a deal colder than they are now,—the northern limit of vegetation therefore much lower than now,—about the epoch when it would seem probable that the existing species of our plants were created. At any rate, during the glacial period, there could have been no phenogamous plants on our continent anywhere near the polar regions; and it seems a good rule to look in the first place for the cause or reason of what now is in that which immediately preceded. I don’t see that Greenland could help us much; but if there was any interchange of species between N. America & N. Europe in those times, was not the communication more likely to be in lower latitudes than over the pole?
If, however, you say—as you may have very good reasons for saying that the existing species got their present diffusion before the glacial epoch, I should have no answer. I suppose you must needs assume very great antiquity for species of plants in order to account for their present dispersion, so long as we cling—as one cannot but do, to the idea of the single birth place of species.
I am curious to see whether, as you suggest, there would be found a harmony or close similarity between the geographical range in this country of the species common to Europe and those strictly representative or strictly congeneric with European species. If I get a little time I will look up the facts,—though as Dr. Hooker rightly tells me, I have no business to be running after side game of any sort, while there is so much I have to do—much more than I shall ever do, probably, to finish undertakings I have long ago begun.
— I wish you would tell me why you were led to conclude a priori, that trees would have a stronger tendency to be mono-diœcious than herbs. 10
As to your P.S.— If you have time to send me a longer list of your Protean genera, I will say if they seem to be Protean here.—11 Of those you mention—
Salix, I really know nothing about.
Rubus: the N. American species, with one exception, are very clearly marked indeed.
Mentha. We have only one wild species! that has two pretty well-marked forms, which have been taken for species: one smooth, the other hairy.
Saxifraga, gives no trouble here.
Myosotis: only one or two species here, and those very well-marked.
Hieracium: few-species; but pretty well-marked.
Rosa: putting down a set of nominal species, leaves us 4: two of them polymorphous, but easy to distinguish.
Our genera which I take to be most Protean (restricting myself to those of Bot. N. U. States) are—Ranunculus, Viola, Lechea, Vitis, Ceanothus, Polygala, Amorpha, Lespedeza, Lathyrus, Cratægus, Amelanchier, Calycanthus, Œnothera, Ribes, Zizia, Viburnum, Galium, Oldenlandia , VERNONIA, Liatris, Eupatorium, ASTER, Erigeron, Solidago, Silphium, Xanthium, Echinacea, Helianthus, Coreopsis, Bidens, Artemisia , SENECIO, Cirsium, Nabalus, Mulgedium, Lobelia, Vaccinium, Azalea, Pyrola, Bumelia, Plantago, Dodecatheon, Lysimachia, Gerardia, Dipteracanthus, Verbena, Lycopus, Pycnanthemum, Monarda, Scutellaria, Stachys, Phlox, Gentiana, Apocynum, Fraxinus, Polygonum, Euphorbia, Acalypha, Celtis, Carya, Quercus, (Salix & Populus, because not well known) ABIES, Sparganium, POTOMAGETON, Sagittaria, Spiranthes, Iris, Smilax, Lilium, Juncus, Commelyna, Tradescantia, Xyris, CYPERUS, Scirpus, Eriophorum, Rynchospora, Scleria, Carex, Agrostis, Panicum, Andropogon.— I have given you both large & small genera—and have marked the worst by underscoring, according to their degree of badness.12
It is not so easy to answer the question in your last P.S.— How I distinguish the introduced & aboriginal stocks of the same species in this country. We have yet a great extent of country in a state of nature,—especially woods. When a plant grows there widely there is no doubt.— While our weeds in cult. lands &c are so generally introduced plants that there is a strong tendency to view them all as such. We have, however, a considerable number of indigenous species becoming weeds. I mean to catalogue them: also some time or other the question will be reared whether they were indigenous to this country. Œnothera biennis, Erigeron annuum & strigosum & Canadense (if really indigenous at the north). Antennaria margaritacea, Asclepias Cornuti, &c—&c
Generally the wild and the introduced stocks look different, more or less, e.g. Triticum repens & caninum, etc—
Sometimes it is mere guess-work, but generally I feel sure, tho’ I could not always tell perfectly well why.
A great many plants came with seed-grain—with cattle, &c—just as they have been carried to various parts of the world— Now these (take Dandelion & Agrostis vulgaris for examples)—these were none the less likely to come here in this way because they were already a part of the indigenous flora!
But I will not ask you to read more of my blind handwriting now. I will not leave your welcome letters so long unnoticed again, if I can help it.
Ever Yours | Asa Gray
Discusses the ranges of alpine species in U. S. and considers the possible migration routes of such species from Europe.
Lists those U. S. genera which he considers protean and describes the U. S. character of some genera which are protean in Europe.
Describes how he distinguishes introduced and aboriginal stocks of the same species.