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Letter 734

Hooker, J. D. to Darwin, C. R.

29 Jan 1844
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    Summary Add

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    Remarks on geographical divisions of the flora of the Southern Hemisphere.

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    JDH beginning Galapagos plants. Value of studying insular floras with respect to inquiries about adaptation of species.

Transcription

West Park Kew

January 29th 1844

My dear Sir

The arrival of your letter this morning put me to shame, for not having answered ere this your former very kind one. You take so much notice of me, that I am almost afraid of saying too much, & of destroying the illusory character you give of my little notes—

Those French works of Voyages are so unsatisfactory, until finished, they come out so irregularly, & are transmitted to our houses so incomplete that as yet I have not been able to make out from D'Orbignys work what particular plants he has described; I find a great deal in scattered parts, but am at a loss as to what countries he intends to fully illustrate. The Botany of Patagonia is entirely cut off as you have remarked from that of Fuegia, & the Chilian coast, in so much so that I thought of considering its Flora seperately, & not connecting it with that of the latter country, further than is avoidable from having a few of its types in the Falkland Islds. No circumstance is so remarkable as the comparative abundance of Leguminosæ along the Patagonian coast, & their almost total absence on the Chilian & Fuegian. This fact your collection illustrates better than any other as your collection of that order from Rio Negro & other Patag. coasts is good. It is however from the absence of most vegetable forms, common to similar Latitudes that the characters of those singular plains should be drawn. Strictly speaking my flora should contain no Patagonian plants, as they belong to Northern types, hardly found to the Southward of the straits, but which increase in number of species as the Southern tropic is approached, as far as the Banda Oriental, where they blend the Brazilian; but the maximum of the Fuegian & highly southern types of vegetation will be found in about 45 S., or perhaps 40, they decrease as Botanical features from thence to Valdivia; but not so southward.—

I cannot but consider the Beeches as important a Bot. feature & guide in S. Am, as the Chestnut forests are on Madeira, the belt of pines in North Asia (vid Map to Wrangel's tour) the Birch in N. America, or any other genus or species which defines the geographical limits of a large amount of other species, of plants. Were such a term allowable, as a name to a book, I should prefer calling such a flora, that “of the Beech districts” of S. America.

The Eastern limit to agree with this definition in the Straits of Magals should coincide with the change in Geolog. formation, & with the Beeches, cease at Cape Negro; as however the Patagonian flora is the Negative one, & characterized by the absence of Beech district forms; some of its peculiar plants are probably also found in the latter & I should include therefore those found on the immediate boundary, as those of Elizabeth Isld & Cape Gregory Bay. The Geological features of K. Charles S. land to the Northd of Admiralty Sound & all to the Westd of that Latitude is I suppose Patagonian in its flora, as well as its Geology. & had I its plants they too should be excluded..— Mr Berkeley was with us shortly before your letter arrived, & I gave him all my Fungi, he has returned me for Mr Henslow your Lichens, which he had; but said nothing about the other orders in his possession, I shall write to him about them.. I found a third species of the curious genus Cyttaria on the deciduous Beech in Hermite Isld. a much smaller species with only 4 cells—

I am now examining the Galapago's plants & shall soon duly report to you on the state of the seeds as to arming, &c. I have begun with the Cryptogamia. Fungi one species, found all over the world. Lichens 2 species both gerontogeous & English; I believe the Tortoise to be the only animal which eats the Usnea plicata; the most common Lichen decidedly in the world. There are no Algæ “hiatus valde deflendus” but the Filices with which I am now working, are very nice, most of them are of course common to S. Am & the W. Indies especially, a few more particularly to the W. coast; a few also are quite new; the difficulty of determining such long neglected tribes is however difficult & I do not speak confidently. I hope soon to present all the Cryptog in a written form to the L. Soc. with descript. of n. sps. Amongst these the number of genera to sp. is very large, as in all circumscribed portions of land. Were there any tree ferns among them? i.e. with short stems?.—

I have notes on the comp. number of sp to gen in various places but they are at the Admiralty, for though I have been 4 months at home they have not yet returned me the notes drawings &c Botanical & others which I gave up as per order. When I receive them I shall tell you what little I have done; the results I think were curious regarding Arctic forms.— These lists are troublesome to make, as species are so loosely described. For instance of the arbor. comp. of St Helena in one genus 5 species are made out of 3, & in another 4 out of 2, which makes a vast difference in so small a flora— on the other hand, the French in D'Urville's last voyage have made 2 genera out of the 2 Antart. Beeches! & neither of them Fagus; true species of which they assuredly both are, as far as the limits of genera can be at all defined.—

You ask me whether I suppose the small proportion of sp to genera in Coral Islets, arises from chance of seeds &c? I cannot answer this, I should say perhaps not:— if genera or small groups are truly natural they are supposed to contain many characters in common, it is but right to assume that the character of transportable seeds should hence be common to some groups above others, the inference I need not state. The seeds of Cruciferous plants do not keep well & this I believe to be a character of the group. Yet Cruciferæ are found all over the world. The presence of some most remarkable plants in several remote isolated spots, staggers all my notions of the migration of species— The Kerguelen's Land cabbage is found only in that Island & is the most remarkable plant of its whole Nat Ord in the whole S. Hemisphere there is nothing at all like it any where else; yet almost all the other Kerg. land plants are Fuegian. Vegetation was doubtless once very different on the same spot to what it is now. Nor do I see that we have any chance of solving the question that relates to the existence of certain plants on Islands created, (we suppose,) before the time of man. That there was a beginning to the creation of plants on our globe is very true, we can hardly suppose that we have now only the remains of that original stock or why should not the said cabbage grow on lands we suppose older than Kerg Land, or the Seychelle double cocoa nut on older formations than they are— There may in my opinion have been a series of productions on different spots, & also a gradual change of species. I shall be delighted to hear how you think that this change may have taken place, as no presently conceived opinions satisfy me on the subject.—

The shells of Antarct regions I should have thought were more proportionally abundant in species than genera— In Kerg Land I procured 3 limpets (no Fissurella) 3 Muscles & one land shell, I think only 2 other sea shells were found; but I had them not, I speak from recollection— In all Southern regions it appeared to me that there were more of those genera Mussels & limpets in proportion to others, than of any one genus of Seaweeds to another; & that by very far; the fact always struck me. All the facts of Nat. Hist. that tend to illustrate insular flora's are to me most interesting, & will prove the most valuable of any toward satisfying enquiry about the adaptation of species to various ends— You are I daresay aware of the fact that there is no reason to believe that plants can be artificially acclimated to any extent— Gardeners have hardly made any plant hardy, either by growing it from seeds of an introduced live specimen which did but just ripen, or by grafting on allied hardier species.—

Many plants seem made to live every where & others no where but where they seem to have been generated.. You may depend upon my best exertions to name the Galapago plants carefully: it is a slow business but I like it much.—

    Footnotes Add

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    f1 734.f1
    Orbigny 1835–47. See letter to J. D. Hooker, [11 January 1844], n. 3.
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    f2 734.f2
    The South American name for the state of Uruguay: literally, the eastern shore of the River Uruguay. CD also used this name, see Journal of researches, p. 169.
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    f3 734.f3
    Ferdinand Petrovich Wrangel. See Wrangel 1840.
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    f4 734.f4
    John Stevens Henslow, who had originally received CD's Beagle plant collections. The plants were subsequently passed to Hooker in the autumn of 1843 (see Correspondence vol. 2, letter from J. D. Hooker, 28 November 1843).
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    f5 734.f5
    See CD's query on hooked seeds in his letter to J. D. Hooker, [11 January 1844].
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    f6 734.f6
    Belonging to the Old World.
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    f7 734.f7
    Hooker did not publish descriptions of CD's Galápagos cryptogams separately. Rather they formed part of J. D. Hooker 1845d, published by the Linnean Society.
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    f8 734.f8
    J. D. Hooker 1844–7, p. 217 n.: I may remark, that species in isolated islands are generally well defined; this is in part the natural consequence of another law which I have observed, that genera in islands bear a large proportion to the species, or in other words, that genera are small, seldom containing more than two or three species, and very frequently solitary representatives.
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    f9 734.f9
    Arborescent Compositae.
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    f10 734.f10
    The beeches were divided into Calucechinus and Calusparassus by Jacques Bernard Hombron in the atlas of plates to Dumont d'Urville [1841–54]. Hooker reallocated Hombron's species in J. D. Hooker 1844–7, pp. 345–9. Later volumes in Dumont d'Urville [1841–54] acknowledge Hooker's corrections, see Decaisne 1853, pp. 7–10.
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    f11 734.f11
    Pringlea antiscorbutica. See J. D. Hooker 1844–7, pp. 238–41, for a fuller description of the Kerguelen Land cabbage. See also plate facing p. 288.
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    f12 734.f12
    A pencil note, written on cream-coloured, unwatermarked paper, 20cm wide, is bound with this letter (DAR 100: 7). The paper seems to have been cut from a sheet of CD's typical 1840s stationery. The note may be a continuation of the annotations to paragraph seven, as it is written in a similar strong hand, pertains to the same passage, and continues to discuss the relation between struggle and diversity: Explanation of fewness of species & diversity of genera, I think must be partly accounted for that plants of diverse groups cd subsist in greater numbers, *& interfere less with each other. [above del illeg] This must be explanation of Arctic Regions.— How are Alpine Plants— Several genera?
    If contemporary, this note is of interest given the closeness of these views to CD's principle of divergence, as explained in a letter to Asa Gray, 5 September [1857], and Origin, pp. 111–26.
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