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From Asa Gray   [early August 1856]

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Summary

Believes intermediate varieties are generally less numerous in individuals than the two states that they connect.

Discusses the difficulties of deciding what is the typical form of a species

and gives some opinions on the variability of introduced species compared with indigenous species.

Author:  Asa Gray
Addressee:  Charles Robert Darwin
Date:  [early Aug 1856]
Classmark:  DAR 165: 93
Letter no:  DCP-LETT-1934

To Asa Gray   24 August [1856]

Summary

Rarity of intermediate varieties.

Variability of introduced plants.

Ranges of plants common to Europe and U. S.

Author:  Charles Robert Darwin
Addressee:  Asa Gray
Date:  24 Aug [1856]
Classmark:  Archives of the Gray Herbarium, Harvard University (36)
Letter no:  DCP-LETT-1944

From Asa Gray   23 September 1856

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Summary

Plants that are social in the U. S. but are not so in the Old World.

Distribution of U. S. species common to Europe.

Gives Theodor Engelmann’s opinion on the relative variability of indigenous and introduced plants and notes the effects of man’s settlement on the numbers and distribution of indigenous plants.

Author:  Asa Gray
Addressee:  Charles Robert Darwin
Date:  23 Sept 1856
Classmark:  DAR 165: 94
Letter no:  DCP-LETT-1959

To Asa Gray   12 October [1856]

Summary

Thanks AG for the first part of his "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]

and for information on social and varying plants.

Would like to know number of genera of introduced plants in U. S.

Is surprised at some affinities of northern U. S. flora and asks for any climatic explanations.

Asks what proportion of genera common to U. S. and Europe are mundane.

Is glad AG will work out the northern ranges of the European species and the ranges of species with regard to size of genera.

Author:  Charles Robert Darwin
Addressee:  Asa Gray
Date:  12 Oct [1856]
Classmark:  Archives of the Gray Herbarium, Harvard University (6)
Letter no:  DCP-LETT-1973

From Asa Gray   4 November 1856

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Summary

Outlines the ranges of northern U. S. species common to Europe. Hopes to investigate the resemblances between the floras of the north-eastern U. S. and western Europe. Discusses routes by which alpine plants appear to have reached U. S.

Author:  Asa Gray
Addressee:  Charles Robert Darwin
Date:  4 Nov 1856
Classmark:  DAR 165: 95
Letter no:  DCP-LETT-1982

To Asa Gray   24 November [1856]

Summary

Variability of naturalised plants.

Distribution of Arctic/alpine plant species.

Limits to the northern range of plants.

Author:  Charles Robert Darwin
Addressee:  Asa Gray
Date:  24 Nov [1856]
Classmark:  Archives of the Gray Herbarium, Harvard University (5)
Letter no:  DCP-LETT-1999

To Asa Gray   1 January [1857]

Summary

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.

Author:  Charles Robert Darwin
Addressee:  Asa Gray
Date:  1 Jan [1857]
Classmark:  Archives of the Gray Herbarium, Harvard University (7)
Letter no:  DCP-LETT-2034

From Asa Gray   16 February 1857

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Summary

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.

Author:  Asa Gray
Addressee:  Charles Robert Darwin
Date:  16 Feb 1857
Classmark:  DAR 165: 96
Letter no:  DCP-LETT-2053

To Asa Gray   [after 15 March 1857]

Summary

Urges AG to generalise from his observations on the flora of the northern U. S.

Expected to find separation of sexes in trees because he believes all living beings require an occasional cross, and none is perpetually self-fertilising. The multitude of flowers of a tree would be an obstacle to cross-fertilisation unless the sexes tended to be separate.

The Leguminosae are CD’s greatest opposers; he cannot find that garden varieties ever cross. Could AG inquire of intelligent nurserymen on the subject?

Thanks AG for information on protean genera; much wants to know whether their great variability is due to their conditions of existence or is innate in them at all times and places.

Author:  Charles Robert Darwin
Addressee:  Asa Gray
Date:  [after 15 Mar 1857]
Classmark:  Archives of the Gray Herbarium, Harvard University (8)
Letter no:  DCP-LETT-2060

From H. C. Watson to Asa Gray   13 March 1857

Summary

Describes problems of classifying species in highly variable genera. Lists highly variable genera. Comments on the list of Asa Gray. Says species may be made to appear more or less variable according to whether a genus is divided into few or many species.

Author:  Hewett Cottrell Watson
Addressee:  Asa Gray
Date:  13 Mar 1857
Classmark:  DAR 181: 36
Letter no:  DCP-LETT-2065

To Asa Gray   9 May [1857]

Summary

Thanks for new part of "Statistics".

Interested in disjoined species; do they tend to belong to large or small genera, and are they generally members of small families?

Is glad AG will tackle introduced plants; has noticed that the proportion of a particular family to the whole flora tends to be similar in introduced and indigenous plants.

Author:  Charles Robert Darwin
Addressee:  Asa Gray
Date:  9 May [1857]
Classmark:  Archives of the Gray Herbarium, Harvard University (9)
Letter no:  DCP-LETT-2089

From Asa Gray   1 June 1857

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Summary

Comments on species with disjoined ranges; does not feel, despite CD’s expectations, that they tend to belong to small families.

Gives the proportion of U. S. trees in which the sexes are separate [see Natural selection, p. 62].

Author:  Asa Gray
Addressee:  Charles Robert Darwin
Date:  1 June 1857
Classmark:  DAR 8: 47bA
Letter no:  DCP-LETT-2098

From Asa Gray   [c. 24 May 1857]

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Summary

Discusses difficulties involved in deciding which genera are protean in the light of some comments by H. C. Watson.

Author:  Asa Gray
Addressee:  Charles Robert Darwin
Date:  [c. 24 May 1857]
Classmark:  DAR 165: 97
Letter no:  DCP-LETT-2104

To Asa Gray   18 June [1857]

Summary

Thanks for AG’s remarks on disjoined species. CD’s notions are based on belief that disjoined species have suffered much extinction, which is the common cause of small genera and disjoined ranges.

Discusses out-crossing in plants.

Has failed to meet with a detailed account of regular and normal impregnation in the bud. Podostemon, Subularia, and underwater Leguminosae are the strongest cases against him.

Author:  Charles Robert Darwin
Addressee:  Asa Gray
Date:  18 June [1857]
Classmark:  Archives of the Gray Herbarium, Harvard University (9a)
Letter no:  DCP-LETT-2109

From Asa Gray   7 July 1857

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Summary

Believes, with CD, that extinction may be an important factor in explaining plant distributions, but sees no reason why the several species of a genus must ever have had a common or continuous area. "Convince me of that, or show me any good grounds for it … and I think you would carry me a good way with you". It is just such people as AG that CD has to satisfy and convince.

Feels that the crossing of individuals is important in repressing variation and perhaps in perpetuating the species, but instances some plants in which it cannot, apparently, take place.

Author:  Asa Gray
Addressee:  Charles Robert Darwin
Date:  7 July 1857
Classmark:  DAR 205.9: 381; DAR 165: 98
Letter no:  DCP-LETT-2120

To Asa Gray   20 July [1857]

Summary

Believes species have arisen, like domestic varieties, with much extinction, and that there are no such things as independently created species. Explains why he believes species of the same genus generally have a common or continuous area; they are actual lineal descendants.

Discusses fertilisation in the bud and the insect pollination of papilionaceous flowers. His theory explains why, despite the risk of injury, cross-fertilisation is usual in the animal and vegetable kingdoms, even in hermaphrodites.

Author:  Charles Robert Darwin
Addressee:  Asa Gray
Date:  20 July [1857]
Classmark:  Archives of the Gray Herbarium, Harvard University (9b)
Letter no:  DCP-LETT-2125

From Asa Gray   [August 1857]

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Summary

States he has "misgivings about the definiteness of species". Believes there is some inherent tendency for plants to originate varieties. Cross-fertilisation is likely in most cases but sees difficulties with plants like Adlumia.

Author:  Asa Gray
Addressee:  Charles Robert Darwin
Date:  [Aug 1857]
Classmark:  DAR 165: 100, 101
Letter no:  DCP-LETT-2129

To Asa Gray   5 September [1857]

Summary

Encloses an abstract of his ideas on natural selection and the principle of divergence; the "means by which nature makes her species".

Discusses varieties and close species in large and small genera, finding some data from AG in conflict with his expectations.

Has been observing the action of bees in fertilising kidney beans and Lobelia.

Author:  Charles Robert Darwin
Addressee:  Asa Gray
Date:  5 Sept [1857]
Classmark:  Archives of the Gray Herbarium, Harvard University (48)
Letter no:  DCP-LETT-2136

To Asa Gray   29 November [1857]

Summary

Thanks AG for his criticisms of CD’s views; finds it difficult to avoid using the term "natural selection" as an agent.

Discusses crossing in Fumaria and barnacles.

Has received a naturally crossed kidney bean in which the seed-coat has been affected by the pollen of the fertilising plant.

Finds the rule of large genera having most varieties holds good and regards it as most important for his "principle of divergence".

Author:  Charles Robert Darwin
Addressee:  Asa Gray
Date:  29 Nov [1857]
Classmark:  Archives of the Gray Herbarium, Harvard University (18)
Letter no:  DCP-LETT-2176

To Asa Gray   21 February [1858]

Summary

Asks whether botanists tend to record varieties more carefully in large genera or small genera.

Wants information on the ranges of varieties of a species compared to the range of the species.

Author:  Charles Robert Darwin
Addressee:  Asa Gray
Date:  21 Feb [1858]
Classmark:  Archives of the Gray Herbarium, Harvard University (21)
Letter no:  DCP-LETT-2218
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