Ɛpsilon

From W. T. Thiselton-Dyer   [before 17 January 1877]1

message as I received it.

A few things occurred to me in reading the Introduction.2 No doubt they have all occurred to you and I merely offer them on the remote chance of their proving useful. The nos: refer to the paragraphs

II. The difference between ♀ & ♂ in some plants is really surprising. In Restiaceæ which are locally abundant in individuals, species, & genera in Australia and at the Cape of Good Hope the sexual differentiation has so far affected the whole plant that Dr Masters and Mr Bentham who have recently studied them—the former as regards Africa the latter as regards Australia—consider it practically impossible to match one ♂ & ♀ of at any rate many species amongst Herbarium specimens3

There is something curious about the “domestic economy” of Petasites vulgaris. I see you have Sir J. Smith’s English Flora and you will find the account of it in vol. iii pp. 426, 427. The species is if one may so put it both monœcious and diœcious. The two Linnean species Tussilago Petasites & Tussilago hybrida are regarded now as the predominantly male and female forms respectively4

By the way you have two Thirdly’s5

iv. There are many hermaphrodite plants which frequently suppress their petals. Ranunculus auricomus is one. This species is often sterile which I find Masters Journ. of Bot. 1867 p. 159, attributes to a tendency found in other Ranunculaceæ to become diœcious.6

vii. It hardly comes within your plan probably to mention the numerous cases in which flowers hang out ‘flags of distress’ without apparently paying any very heavy price for it.— In many Cruciferæ the external flowers of the corymbs are developed in a way comparable with that in Compositæ and Umbelliferæ. In Iberis there are certainly the proper proportion of stamens in the enlarged flowers though it is possible they may not be up to much.7

diagram

But the most singular arrangement I know is in Mussænda a genus of Rubiaceæ where one tooth of the calyx in a few flowers of an inflorescence is developed into a large leafy expansion8 Something (I am drawing from memory like this)  I am not prepared to say without disturbing herbarium specimens what effect this may have had on the sexual organs

diagram

As you mention the singular arrangement in Muscari one calls also to mind cases like Salvia Horminum where the upper bracts are enlarged and brightly coloured and the flower suppressed. The same arrangement obtains also in Lavandula and other Labiates9

Believe me | Yours very truly | W. T. Thiselton Dyer

incomplete

CD annotations

1.1 message … it.] del pencil
2.1 A few … paragraphs 2.3] crossed ink
3.1 In … specimens 3.6] ‘Bentham cd tell me whether rudiments of sexual organs’ added pencil
4.1 There is … Labiates 9.5] crossed ink
4.3 The two … respectively 4.5] scored pencil
6.1 iv. … is one. 6.2] scored pencil
7.4 Cruciferæ] underl pencil
9.2 Salvia Horminum] ‘& [Masters] case of’ added pencil
9.2 Salvia … suppressed. 9.4] scored pencil; ‘Ballardia is next genus to muscari & Hyanthus’ added ink
Top of letter: ‘p 3 gradation of dioiceous Plant Tussilago’ pencil
Verso of last page: ‘[‘Umb’ del] Iberis | Mussænda— | Your praise of my book pleases me much, though I fear it is greatly too strong.— [‘My object’ del] I am particularly obliged for your notes,— my object I feared that I might have fallen into the grossest errors— I’10 pencil del blue crayon
1
The date is established by the relationship between this letter and the letter to W. T. Thiselton-Dyer, 17 January 1877.
2
CD evidently sent a manuscript copy of the introduction to Forms of flowers to Thiselton-Dyer for his comments; the manuscript has not been found.
3
Restiaceae (a synonym of Restionaceae) is a large family of rush-like flowering plants of the southern hemisphere. Maxwell Tylden Masters, in his ‘Synopsis of the South African Restiaceæ’, had noted that considerable confusion had been caused by authors describing as distinct species what proved to be the opposite sex of some previously described genus or species (Masters 1867a, pp. 209–10). George Bentham had similarly stated that the great dissimilarity in habit and inflorescence between the males and females of some species made even their generic determination very difficult (Bentham and Mueller 1863–78, 7: 209). In the published version of Forms of flowers, p. 11, CD added Thiselton-Dyer’s observation in discussing dioecious plants.
4
In his description of Petasites, James Edward Smith synonymised Tussilago petasites L. with Petasites vulgaris (a synonym of P. hybridussubsp. hybridus, butterbur) and described the moneocious form as a casual variety. The species is usually dioecious, but sometimes monoecious. CD’s annotated copies of the first four volumes of J. E. Smith 1824–36 are in the Darwin Library–CUL.
5
In the published version of the introduction to Forms of flowers, CD does not use the term; rather, he refers to the first to fourth classes of polygamous plants.
6
Ranunculus auricomus (goldilocks buttercup) has imperfect or frequently absent petals. Masters had noted the frequent sterility of this and similar species in a discussion of the morphology of the ovules of Ranunculus (Masters 1867b).
7
Iberis is the genus of candytuft in Cruciferae (a synonym of Brassicaceae), the mustard and cabbage family. Compositae is a synonym of Asteraceae, the daisy and sunflower family. Umbelliferae is a synonym of Apiaceae, the carrot and parsley family.
8
Mussaenda is a genus of tropical Indian and African plants in the family Rubiaceae (coffee and madder). In Forms of flowers, p. 5, CD described the flowers as characterised by a single modified sepal with large petal-like expansion.
9
In the published version of Forms of flowers, p. 8, CD cited Thiselton-Dyer for his information on Salvia horminum (a synonym of S. viridis, annual clary). CD had also described the modified bud-like flowers of Muscari or feather hyacinth (now more commonly referred to as grape hyacinth).
10
CD’s annotations are notes for his reply; see letter to W. T. Thiselton-Dyer, 17 January 1877.

Please cite as “DCP-LETT-10757,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-10757