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Darwin Correspondence Project

To Asa Gray   16 February [1862]1

Down Bromley Kent

Feb. 16th

My dear Gray

I have been trying a few experiments on Melastomatads;2 & they seem to indicate that the pollen of the two curious sets of anthers (ie the petal-facers & the sepal-facers) have very different powers; & it does not seem that the difference is connected with any tendency to abortion in the one set.— Now I think I can understand the structure of flower & means of fertilisation, if there be two forms,—one with the pistil bent rectangularly out of the flower, & the other with it nearly straight. Study the enclosed magnificent diagram!3 Our hot-house & green-house plants have probably all descended by cuttings from a single plant of each species; so I can make out nothing from them. I applied in vain to Bentham & Hooker;4 but Oliver picked out some sentences from Naudin, which seem to indicate differences in the position of the pistil.5

I see that Rhexia grows in Massachusetts; & I suppose has two different sets of stamens. Now, if in your power, would you observe the position of the pistil in different plants, in lately-opened flowers of the same age (I specify this because in Monochætum I find great changes of position in the pistils & stamens, as flower gets old).6 Supposing that my prophecy should turn out right, please observe whether in both forms the passage into the flower is not in the upper side of the pistil, owing to the basal part of the pistil lying close to the ring of filaments on the under side of the flower.— Also I should like to know the colour of the two sets of anthers.—7

This would take you only a few Minutes & is the only way I see that I can find out whether these plants are dimorphic in this peculiar way, i.e. only in the position of the pistil & in its relation to the two kinds of pollen.— I am anxious about this, because if it should prove so, it will show that all plants with longer & shorter or otherwise different anthers, will have to be examined for dimorphism.—

Will you keep this note as a memorandum? You see that I do not scruple to trouble you.— I am tired tonight, so will write on no other subject.—

Ever yours most truly | C. Darwin

[Enclosure]

[DIAG HERE] Corolla removed One stamen of each kind alone represented projection to anthers sepal-facing anther   yellow Supposed position of pistil in second Form petal-facing anther   purple pistil sepals (The yellow anthers give far more seed than the purple anthers.)8

Footnotes

The year is established by the relationship to the letter from Asa Gray, 6 March [1862].
CD began to experiment with the melastomaceous plant Heterocentron roseum in October 1861 (see Correspondence vol. 9, letter to J. D. Hooker, 17 November [1861], and this volume, letter to George Bentham, 3 February [1862] and n. 8). He had also recently started crossing experiments with Monochaetum ensiferum (see letter to J. D. Hooker, 9 February [1862] and n. 7). There are dated notes from these experiments in DAR 205.8.
See enclosure.
CD recorded this observation in a note dated 12 February 1862 (DAR 205.8: 23).
For Gray’s agreement to carry out observations on Rhexia, see the letter from Asa Gray, 6 March [1862].
CD refers to the results of a crossing experiment with Heterocentron roseum, begun in October 1861 and harvested in February 1862. There are dated notes from this experiment in DAR 205.8: 44–6. See also letter to George Bentham, 3 February [1862] and n. 8. This drawing is apparently a composite based on the drawing of Heterocentron roseum, dated 29 October 1861, in DAR 205.8: 45, and the drawings of Monochaetum ensiferum, dated 15 January and 12 February 1862, in DAR 205.8: 22–3. See also letter to Asa Gray, 15 March [1862] and n. 10. The diagram has been reduced to 75% of its original size.

Summary

Floral structure of Melastoma. Asks AG to observe position of pistils in lately-opened flowers of different plants.

Letter details

Letter no.
DCP-LETT-3448
From
Charles Robert Darwin
To
Asa Gray
Sent from
Down
Source of text
Gray Herbarium of Harvard University (63)
Physical description
4pp diag

Please cite as

Darwin Correspondence Project, “Letter no. 3448,” accessed on 16 July 2019, http://www.darwinproject.ac.uk/DCP-LETT-3448

Also published in The Correspondence of Charles Darwin, vol. 10

letter