From Philip Henry Gosse   30 May 1863

Sandhurst. Torquay

May 30. 1863

My dear Sir

Will you kindly vouchsafe me a little word of help. With your charming book before me, I have been trying to fertilise the Orchids of my little collection, as they flower.1 With some I succeed, with others there is difficulty. Let me tell you of the present “fix”.

Stanhopea oculata opened four great blooms on Thursday: today they begin to flag, & I delay no longer to impregnate. I reach down your book, turn to your figure at p. 179,2 & recognise the parts well enough. Then with a toothpick I lift the anther, & out come the pollinia very well depicted by you at p. 185 fig C;3 except that in this species the poll. masses are much larger in proportion to the visc. disk. The disk is viscid enough, & I carry the whole on the toothpick. Now I want to find where to deposit it; I take for granted that it is in the hollow (marked a in my sketch,4 wh. is the stigma. But there is no viscosity there, nor anywhere near, up or down, not the slightest; & I cannot get the pollinia to adhere.5 How can this plant be fertilised? And how wd. any insect do it? & what wd. an insect be about, to touch the tip of this isolated projecting column? Supposing the great bee, or Scolia,6 or what not, wants to get at the hollow hypochil7 (tho’ I don’t find any honey there), he wd. alight on the epichil8 whose surface is already three fourths of an inch from the rostellum, & which being moveable wd. bend away still further,—& creep between the horns of the mesochil:—9 how thus could he touch the anther? & if he did, how cd. he lodge the pollen on the stigma? & if he did, how cd. it stick, seeing the place is not sticky?

Do resolve me these doubts; & believe me, | My dear Sir | Ever yours truly | P. H. Gosse

The disk at the end of the caudicle adheres to the stigma, but the pollen masses project, & won’t touch it, tho’ pressed against it with force.

Charles Darwin Esqe.

1
Gosse refers to Orchids. Although primarily a zoologist, Gosse devoted much time during his later years to the study of orchids (R. Desmond 1994).
2
Figure 22 (Orchids, p. 179) is a longitudinal section showing the structure of the column in the Vandeae. The column of an orchid flower is formed of three carpels, and generally four stamens, all confluent.
3
Figure 23 (Orchids, p. 185) depicts the pollinia of four species of Vandeae; ‘c’ depicts the pollinium of Stanhopea saccata ‘after depression’. It shows the two pollen masses, their mutual stipe, and the viscid disc at its base.
4
The sketch has not been found.
5
For pollination to be effected, the pollen masses or individual pollen grains must adhere to the stigma.
6
Scolia flavifrons (a synonym of Megascolia maculata subsp. flavifrons), the yellow-fronted digger wasp, is the largest European species of Hymenoptera (Grzimek ed. 1975, pp. 424–5).
7
The hypochil is the basal part of the labellum, usually the largest of the three petals, of an orchid flower (Bailey and Bailey 1976).
8
The epichil is the terminal part of the labellum of an orchid (Bailey and Bailey 1976).
9
The mesochil is the intermediate part of the labellum in those orchids that have the labellum separated into three distinct parts. The rostellum is an extension of the upper edge of the stigma of an orchid, forming a flap of sterile tissue separating the stigmatic surface from the anthers in the column (Bailey and Bailey 1976).

Please cite as “DCP-LETT-4194,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-4194