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Darwin Correspondence Project

From Asa Gray   21 November 1870

Botanic Garden, | Cambridge, Mass.

Nov. 21. 1870

My Dear Mr. Darwin

I have been a long while studying a family of plants, the Polemoniaceæ, in the flowers of which I see, now and then, what ought to be dimorphism of the Primula sort, yet not complete or reciprocal.1

One of the best-marked cases is that of Gilia (Leptosiphon) nudicaulis (= Collomia nudicaulis Hook. & Arn.)2 The style in some individuals is very long and more or less exserted; in others short and deeply included in the tube of the corolla. But the stamens are the same in both, i.e. the anthers sessile in the throat. G. (Leptosiphon), androsacea3—common in cultivation has generally long style,—sometimes a short one, And I think I have seen the short style in some others of the group.

In the Ipomopsis section of Gilia (as I limit it) there are 3 species.4

1. G. coronopifolia—with no dimorphism that I can see, but with stamens & style exserted.

2. G. aggregata (pulchella), with stamens in some included in the throat and the style much shorter, i.e. the stigmas lower; others, and more of them, with the stamens exserted, and the style also,—as long or longer.5

3. G. subnuda, a n. sp. of few known specimens—all uniform, with included stamens & more included style.—like the one form of G. aggregata.

Most Gilias show no attempt at dimorphism.

In one group of 2 species, the stamens (inserted, as is common, just under the sinuses of the corolla,) are so remarkably long that I looked for & expected to see a counterpart form with short filaments or lower-inserted ones.6 Nothing of the sort is seen. The styles are neither particularly long nor short.

In Polemonium cæruleum—hardly in any other, the stamens, & I think the style with them, varies more or less in proportion to the corolla—but not in any decided way so that I can sort the dried specimens into two kinds.7

Finally in Phlox, the stamens are on one plan in all,—included, inserted as you know at unequal heights, or the uppermost 2 or even 3 anthers just protruding their tips from the orifice. But the style in each species is either long (the stigmas exserted or barely included) or short, & when so generally very short, so as to leave the stigmas low down in the tube, below or on a level with the lowest anthers.8

As I went on with the study of the species I took with me a foregone conclusion that this was a char. of dimorphism, and therefore would not use it as specific or sectional.

And one common species, P. subulata, seemed to confirm this view of it. I am obliged to regard as the same species P. nivalis (P. Hentzii), which has no obvious difference that I can rest on except a short, I think rather variably short, style.—9 But also generally a pair of ovules in each cell, while ordinary P. subulata has only one. Yet the differences are not absolute, some short-styled ovaries having solitary ovules in one or two (I am not sure if in all 3) of the cells. Here, you see, if the char. of style and ovules corresponded completely, I should have recognised two species. Is dimorphic variation here going on to set up two independent species.—not interbreeding?

And then, all through, what is the good of the variation in length of style the stamens not reciprocating.? or when the stamens vary being long and short with the style? All this is something for you to consider when you are done with Man and such comparatively uninteresting subjects.10

These either long or short styles are strongly marked in all the far-western species, and only one way in each species in all the specimens (very many in some cases) I have examined. So that I am obliged here to take the style as a specific character.11 The annual species, all have short style, & 3 or 4 of the Western perennial ones. The long style is the case in the greater number of the species.

If more of the species were decidedly dimorphic, or were so in an orthodox way (with regular longs and shorts), as in Primula, I should conclude that we had here cases of dimorphism manqué—like what Scott notes of Primula, a few species of which are in the same case.—12 Unless, by an odd combination of chances one sort only of each has been collected. Or, has one sort been so much more prolific than the other, that the less fertile has died out, and the other got insects to fertilise it perfectly from individual to individual of the same sort?

Well, there are the main facts. We are all agog now, waiting for your book on Man. Being out of my line, I shall not see early sheets, and get a perusal in advance.13

We have now been at home a year,—14 a very busy year it has been with me, and not an idle day, hardly. Yet I look back with dismay upon the small amount of work I have accomplished. Mrs. Gray is always delicate, of late very much so. She desires most affectionate regards to you and all your kind family,— it seems a long, long while ago our most delightful visit two years ago.15

Did you see Mr. Morgan of Rochester, N.Y.? He asked for an introduction to you, which I gave, telling you were not always well enough to see any one.16

Ever Yours faithfully | Asa Gray

CD annotations

1.1 I have … longer. 5.3] crossed pencil
2.1 One … throat. 2.4] scored red crayon
5.1 2.... longer. 5.3] scored red crayon
5.1 G. aggregata] underl red crayon
6.1 3.... aggregata. 6.2] crossed red crayon
7.1 Most … kinds. 9.3] crossed pencil
9.1 Polemonium cæruleum] underl red crayon
10.2 or the … anthers. 10.5] scored red crayon
11.1 As … subjects. 13.4] crossed blue crayon
12.1 P. subulata,] under red crayon; ‘X’ added red crayon
12.1 I am … only one. 12.4] scored red crayon
12.4 Yet … interbreeding? 12.8] scored blue crayon
14.4 annual species,] underl red crayon
14.4 The long … species. 14.5] scored red crayon
15.1 If more … Man. 16.1] crossed blue crayon
17.1 We have … any one. 18.2] crossed red crayon
Top of letter: ‘Variable Pistils. | Also case of Variability’ ink; ‘(Kew)’ red crayon; ‘[cross fertilising] | of stamens & Pistils’ blue crayon; ‘See paper Proc. Amer. Soc. of Arts & Sciences’ pencil
Top of 2d sheet: ‘Variability’ blue crayon; ‘Variable length of style only point certain’ pencil; ‘Ask for [illeg]red crayon


Primula has one flower form with a short style and long stamens, and another with a long style and short stamens; see CD’s paper ‘Dimorphic condition in Primula. Gray’s paper, ‘Revision of the North American Polemoniaceae’ (Gray 1870) was read at the 14 June meeting of the American Academy of Arts and Sciences; he gave a general discussion of ‘incipient dimorphism’, including genera mentioned in this letter, on page 248. For a modern classification of the family Polemoniaceae (phlox or Jacob’s ladder), see Grant 1998.
Gray divided Gilia species into groups or sections, one of which was Leptosiphon (Gray 1870, p. 265); Leptosiphon is now the genus Linanthus. Gilia and Collomia are now placed in different tribes of the subfamily Polemonioideae (Grant 1998, p. 742). CD referred to Gray’s description of Gilia nudicaulis (now Linanthus nucidaule) in Forms of flowers, p. 119. Collomia nudicaulis is now Gymnosteris nudicaulis.
See Gray 1870, p. 265. Gilia androsacea is now Linanthus androsaceus.
See Gray 1870, pp. 275–6.
In Gray 1870, p. 275, Gray wrote: ‘the tendency to dimorphism, of which there are traces, or perhaps rather incipient manifestations in various portions of the genus, is most marked in G[ilia]. aggregata’. CD quoted him in Forms of flowers, p. 118. Gilia aggregata, now Ipomopsis aggregata (scarlet gilia), includes a number of subspecies. Gilia coronopifolia is now Ipomopsis rubra.
Gray refers to his group Giliandra, which included Gilia stenothrysa (narrowstem or Uinta Basin gilia) and G. piniitifida (sticky gilia) (Gray 1870, p. 276).
See Gray 1870, p. 281.
For Gray’s description of Phlox species, see Gray 1870, pp. 248–58.
See Gray 1870, pp. 248, 252. CD referred to Gray’s conclusions on Phlox subulata and P. nivalis in Forms of flowers, p. 120. The two are now considered separate species.
CD was finishing Descent.
Gray refers to the westernmost areas of the United States; most members of Polemoniaceae are in western North America.
In his discussion of dimorphic Primula species, John Scott noted several species that appeared to be short-styled and others that appeared to be long-styled, as well as six that he considered non-dimorphic but that sometimes presented variable style and stamen lengths (J. Scott 1864, pp. 80–3).
Gray had read proof-sheets of Variation (see Correspondence vol. 15, letter to Asa Gray, 16 October [1867]).
Gray and his wife, Jane Loring Gray, visited England from September 1868 to November 1869, also travelling on the Continent (J. L. Gray ed. 1893, 2: 565; see also Correspondence vols. 16 and 17).
The Grays and others visited Down House between 24 and 30 October 1868 (Emma Darwin’s diary (DAR 242)).
Gray refers to Lewis Henry Morgan. See letter from L. H. Morgan, 9 August 1870, and letter to L. H. Morgan, 11 August [1870].


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 26 vols to date. Cambridge: Cambridge University Press. 1985–.

‘Dimorphic condition in Primula’: On the two forms, or dimorphic condition, in the species of Primula, and on their remarkable sexual relations. By Charles Darwin. [Read 21 November 1861.] Journal of the Proceedings of the Linnean Society (Botany) 6 (1862): 77–96. [Collected papers 2: 45–63.]

Forms of flowers: The different forms of flowers on plants of the same species. By Charles Darwin. London: John Murray. 1877.

Grant, Verne. 1998. Primary classification and phylogeny of the Polemoniaceae, with comments on molecular cladistics. American Journal of Botany 85: 741–52.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Reports case of apparent incipient dimorphism. Observations on variations in flower structure, especially style length, within species of Polemoniaceae.

Letter details

Letter no.
Asa Gray
Charles Robert Darwin
Sent from
Botanic Garden, Cambridge, Mass.
Source of text
DAR 110: B70–3
Physical description
8pp ††

Please cite as

Darwin Correspondence Project, “Letter no. 7378,” accessed on 28 January 2020,

Also published in The Correspondence of Charles Darwin, vol. 18