Thanks AG for 2d part of "Statistics [of the flora of the northern U. S.", Am. J. Sci. 2d ser. 22 (1856): 204–32; 2d ser. 23 (1857): 62–84, 369–403].
Is glad AG concludes species of large genera are wide-ranging, but is "riled" that he thinks the line of connection of alpine plants is through Greenland. Mentions comparisons of ranges worth investigating.
Believes trees show a tendency toward separation of the sexes and wonders if U. S. species bear this out. Asks which genera are protean in U. S.
Down Bromley Kent
My dear D
I have received the 2
One of your conclusions makes me groan, viz that the line of connection of the strictly
Alpine plants is through Greenland: I sh
In reading your paper, one point struck me as well worth working out, if it could
be done, viz a comparison of the principal zone of habitation in the
U. States of the 320 European plants in comparison with your
115 representative species + the 15 strongly marked varieties =
130 species; & there again rudely with the (4
Overworked as you are, I daresay you will say that I am an odious plague;—but here is another suggestion! I was led by one of my wild speculations to conclude (though it has nothing to do with geograph. distribution, yet it has with your Statistics) that Trees would have strong tendency to have flowers with dioicous, monoicous or polygamous structure. Seeing that this seemed so in Persoon, I took our little British Flora, & discriminating trees from Bushes according to Loudon, I have found that the result was in species, genera & Families, as I anticipated. So I sent my notions to Hooker to ask him to tabulate N. Zealand Flora for this end, & he thought my result sufficiently curious, to do so; & the accordance with Britain is very striking, & the more so, as he made 3 classes of Trees, Bushes, & herbaceous plants.— (He says further he shall work the Tasmanian Flora on same principle.) The Bushes hold intermediate position between the other two classes.— It seems to me a curious relation in itself, & is very much so, if my theory & explanation are correct.
With hearty thanks | Your' most troublesome friend | Ch. Darwin
Pray do not forget variability of Naturalised plants.—
P.S. | You might give me a valuable piece of information, with very little
trouble to yourself.— I have been comparing, as far as I can, Protean genera,
& have left off in a maze of perplexity. By Protean genera, I mean such as
hardly two Botanists agree in about the species,—what to call species
& what varieties. Now what I want to know is, whether such genera as Salix,
Rubus, Rosa, Mentha, Saxifraga, Hieracium, Myosotis, &c have equally Protean
species in U. States; even if they have only one, but more especially if they
have many. I think you have no Rosa, & I forget how it is with some of the other
genera.— The converse case w
- f1 2034.f1Dated by the relationship to the letter from Asa Gray, 16 February 1857.
- f2 2034.f2A. Gray 1856–7.
- f3 2034.f3In his letter to Asa Gray, 2 May , CD had asked Gray to examine the ranges of species in large and small genera of North American plants. CD expected large genera to include the most successful, and hence most common and most widely ranging, forms. CD had previously found some support for his views in A. de Candolle 1855, but Alphonse de Candolle's evidence was not clear-cut because, CD believed, his comparison had been based on families rather than on genera. Gray had compared the species common to North America and Europe, first using families and then genera, and had concluded: ‘To be of any value, at least upon our limited scale, the comparison should be made with genera, as Mr. Darwin suggests’ (A. Gray 1856–7, p. 77).
- f4 2034.f4See Natural selection, pp. 140–67, in which CD discussed ‘the relation of the commonness and diffusion of species to the size of the orders and genera in which they are included’. See also J. Browne 1980.
- f5 2034.f5In mentioning CD's views, Gray stated that ‘from some investigations of his own, this sagacious naturalist inclines to think that species in large genera range over a wider area than the species of small genera do.’ (A. Gray 1856–7, p. 77).
- f6 2034.f6Comparing the northward range of species common to North America and Europe, Gray concluded that ‘it seems almost certain that the interchange of alpine species between us and Europe must have taken place in the direction of Newfoundland, Labrador and Greenland, rather than through the polar regions’ (A. Gray 1856–7, p. 73). CD, on the other hand, believed that a circumpolar flora had travelled only in a north–south direction to colonise lands in lower latitudes (Natural selection, pp. 539–42). See also letter from Asa Gray, 16 February 1857.
- f7 2034.f7CD refers to the section entitled ‘Comparison of the flora of the northern United States with that of Europe in respect to the similar or related species’ (A. Gray 1856–7, pp. 78–84), in which Gray described five different categories of representative species: geographical varieties, very closerepresentative species, strictly representative species, strictly congeneric species, and divergent congeneric species.
- f8 2034.f8Persoon 1805–7 and Loudon 1842 (see Natural selection, pp. 61–2). For Gray's response to this query, see letter from Asa Gray, 1 June 1857.
- f9 2034.f9See letters to J. D. Hooker, 1 December  and 10 December , and letter from J. D. Hooker, 7 December 1856.
- f10 2034.f10CD had continued to remind Gray about this topic after having first mentioned it in his letter to Asa Gray, 2 May . See also letters to Asa Gray, 24 August  and 24 November , and letter from Asa Gray, 4 November 1856.