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 M^r. 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