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Darwin Correspondence Project

From Asa Gray   22 May 1877

Herbarium of Harvard University, | Botanic Garden, Cambridge, Mass.

May 22 1877

My Dear Darwin

I asked my good correspondent Prof. Bessey to see if Lithospermum longiflorum (= angustifolium) being cleistogenous later, is, like its relatives, also dimorphous.1 Here is his first reply just in season to send to you by this post.

I forgot to ask him to examine pollen. I will do so.

Yours ever | Asa Gray


Iowa Agricultural College. | Ames,

May 19th 1877

My dear Doctor Gray.

As to the dimorphism of Lithospermum longiflorum, Spreng. or L. angustifolium Michx. I send you measurements made upon freshly gathered specimens this morning.

I examined ten flowers from five different plants; enough to show that if there is any dimorphism it is a wonderfully irregular one.2 I copy my notes entire.

Plant No 1. { Length of Calyx .32 inch
Flower No 1. " " Corolla 1.04 " (tubular portion only)
" " Style 1.03 " (from base of corolla)
" to middle of anthers .87 "
" of anthers .10 "
Pollen falling freely from anthers.
Flower No 2 Calyx .32
Corolla 1.00
Style 1.00
Stamens .82
Length of anthers .10
Pollen falling freely.
Stamens irregular in height: From top of uppermost to bottom of lowermost .15 inch
Plant No 2. Flower 3d. Calyx .35
Corolla 1.08
Style 1.08
Stamens .93
Anthers .08
Anthers dried up and old.
" Flower 4th. Calyx .35
Corolla 1.18
Style 1.06
Stamens 1.03
Anthers placed irregularly, old and dried up.
Plant No 3. Flower 5th. Calyx .30
Corolla 1.09
Style .92
Stamens .95
Anthers .06
Anthers old and dried up.
" Flower 6th. Calyx .31
Corolla 1.14
Style .95
Stamens .98
Anthers .09
Pollen falling freely.
Plant No 4 Flower 7th Calyx .39
Corolla 1.37
Style 1.05
Stamens 1.20
Anthers old and dried up.
The corolla fell as the flower was plucked.
Flower 8th. Calyx .39
Corolla 1.30
Style 1.19
Stamens 1.17
Flower in “full bloom” possibly a little past.
Stamens of irregular height. Stigma in the midst of the anthers, and covered with pollen. Corolla 4 lobed! Anthers 4! Sepals of irregular size, one only23 the size of the others.
Flower 9th. Calyx .32
Corolla 1.18
Style 1.03
Stamens 1.05
Anthers .06
Anthers shedding pollen, and of irregular height.
Plant 5. Flower 10th. Calyx .39
Corolla 1.06
Style .83
Stamens .90
Flower old.
Calyx with five perfect sepals, and an additional one alternating with and within the normal whorl: this extra one smaller than the others and with yellow petaloid edge.
Flower 11. Calyx— .34
Corolla— 1.15
Style .51
Stamens .97
Anthers .07
This flower had 6 perfect sepals, 6 slightly irregular corolla lobes, and 6 stamens. The short style appeared to be abortive, possibly from an injury, as the stigmatic end was black, and not lobed. Pollen falling freely from the anthers.
Note. Two other flowers (young) on this plant had a 6-sepaled calyx. One had a 6-lobed corolla, both had but 5 stamens each.3

In order to show at a glance the relative lengths of corolla tube, style and stamens, I have constructed these diagrams. They are magnified ten times. Every inch in diagram represents .10 inch actual. To save space the lower six inches of the diagrams are cut off.

I will make further measurements as I have the time, but these show that there is great irregularity in these flowers. I notice that in the forms where the styles are generally shorter than the stamens—the styles are much longer than the stamens in the bud.

I think the small flowers (late ones) are cleistogamous.4 Will watch them when they appear.

This long flowered form seems to be thrown into a state of confusion by the vice of self-fertilization which is almost certainly indulged in by the small flowered forms. The long ones appear to be trying to be heterostylous, but are probably balked by the habits of the short ones.

Very truly | C. E. Bessey.

Thanks for pamphlets. I’ll inquire about artichokes.


Charles Edwin Bessey. Gray had informed CD that Lithospermum longiflorum became cleistogenous later in the season, but was probably not dimorphic (letter from Asa Gray, 30 March 1877). Lithospermum longiflorum and L. angustifolium are synonyms of L. incisum (fringed gromwell). Gray used the non-standard term cleistogenous instead of cleistogamic; see also letter from J. V. Carus, 22 March 1877, n. 2.
In Forms of flowers, p. 3, CD cautioned that mere variability in the floral organs did not automatically mean the forms were truly distinct.
The diagram is reproduced at 80 per cent of its original size.
Forms of flowers 2d ed., p. xix, edited by Francis Darwin, confirmed that Lithospermum longiflorum had cleistogamic flowers, based on Bessey’s later published work on the subject (Bessey 1878).


Forms of flowers 2d ed.: The different forms of flowers on plants of the same species. 2d edition. By Charles Darwin. London: John Murray. 1880.

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


Asked C. E. Bessey whether Lithospermum longiflorum was dimorphic like its relatives. Encloses CEB’s reply.

Letter details

Letter no.
Asa Gray
Charles Robert Darwin
Sent from
Herbarium of Harvard
Source of text
DAR 110: B53–7, DAR 165: 196
Physical description
ALS 2pp, encl ALS 5pp

Please cite as

Darwin Correspondence Project, “Letter no. 10969,” accessed on 16 September 2023,