To J. D. Hooker   18 October [1861]

Down Bromley Kent

Oct 18th

My dear Hooker.

The Book of Reichenbach is that which you told me of “de pollinis Orchid. genesi et structura: Leipsic. 4to.”—1

I am so glad that you can let me have a flower (two if possible) of Catasetum; & for buds of Oncidium.

Please thank Oliver for looking to nectary of Stanhopea.—2

The Acropera came quite fresh. The use of strange Labellum has, as might have been expected, utterly beaten me; the viscid disc forms a cap at end of filamentary rostellum & this I have not seen before; & to remove pollinia well, this must be upturned & brushed upwards; & I fancy Labellum may be concerned in leading insect to depart by this course. But there is one point which considerably interests me, namely that the opening in all the flowers of the stigmatic cavity was too small for end of pollen-mass to enter. Hence I suspect it subsequently enlarges; this I shd. much like to ascertain & therefore shd. be very glad of a few old flowers.—3

Why I wish this, is, because I have found other structures compelling old flowers to be fertilised always by younger flowers.— Spiranthes is a very good case; & Asa Gray who has been looking at N. American species, & did not know of movement of Labellum, was astonished at facility with which pollen-masses could be removed, & at impossibility, as it seemed to him, of the flower being ever fertilised.—4 It is funny on what trifles the fertilisation of Orchids depends; Humble-bees alight at bottom of spike & crawl up Spiranthes; if they were to crawl down, very few flowers would be fertilised.— I long for Catasetum to test points of sensitiveness; Sowerby has made very nice drawings of outside & section.5

I have just been collecting seed of 2 wild species of Verbascum: some time tell me whether you can give me white & yellow var s. of any species: & perhaps I could buy some other species; though I can find none in my few Nursery-Garden Catalogues. I am sure you will agree in importance of testing Gärtner’s statement about the potency of their pollen.6 Also can you give me seed of any Cinchoneæ? & a hairy Saxifrage.7 You see I take you at your word & fully trust your goodnature.

Yours affecy | C. Darwin

Endorsement: ‘/61’

3
See letter to J. D. Hooker, 15 October [1861]. CD discussed this point in Orchids, stating that the stigmatic chamber in Acropera was so narrow that the pollen-masses could ‘hardly be forced in’, making pollination appear a great difficulty (Orchids, p. 205).
4
Asa Gray’s comments on Spiranthes were included in the missing section of the letter from Asa Gray, [27 and 29 August] and 2 September [1861]. See CD’s response to Gray’s remarks in his letter to Asa Gray, 17 September [1861]. For CD’s discussion of the means of pollination in Spiranthes, see Orchids, p. 123.
5
George Brettingham Sowerby Jr’s drawings of Catasetum saccatum appear in Orchids, pp. 216 and 217.
6
Gärtner 1844, pp. 137–8, and Gärtner 1849, pp. 92, 180–1, 724–8. Karl Friedrich von Gärtner had shown that the pollen of white and yellow varieties of particular Verbascum species had different potencies when crossed with other Verbascum species (see letter to J. D. Hooker, 28 September [1861] and n. 11). CD mentioned Gärtner’s findings in his paper ‘On the two forms, or dimorphic condition, in the species of Primula, and on their remarkable sexual relations’ (Collected papers 2: 59) and in Variation 2: 93, 104–7. For CD’s extensive notes on Gärtner 1844 and 1849, see Marginalia.
7
See letters to J. D. Hooker, 19 June [1861] and 28 September [1861].

Manuscript Alterations and Comments

1.2 structura] ‘a’ below ‘a’
4.1 strange] interl
4.2 the] ‘t’ over ‘T’
4.5 depart] after del illeg
4.5 by this course.] interl
5.5 at impossibility] ‘at’ interl
5.5 ever] interl
5.8 points of] interl
6.5 potency of their] interl

Please cite as “DCP-LETT-3288,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-3288