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Darwin Correspondence Project

From Robert Caspary   [after 9 June 1866]1

– – been open for some days certainly and 4 were not yet quite open), giving altogether 1182 grains, amongst them 30 bad ones; this gives 2,5/100 bad grains; but this result is not fair, as I took in account all bad grains I could find, but only those few good ones—comparatively speaking—which happened to be with the bad ones on the same fields of the Microscope. Therefore the percentage of bad grains is still less than 2,5.2 I repeat the percentage of all:

good grains bad grains

Cytisus purpureus 92,3 7,7

— Laburnum 93,3 6,6

— alpinus 96,3 3,73

— Watereri 79,7 20,3

— purp.-elong. 15,2 84,8

— Adami 97,5 2,5

or rather more. or rather less.4

The worst of all as regards the pollen is therefore Cytis. purp.-elong. then Cyt. Watereri; better than all Cytisus Adami. I found allways as often as I examined the pollen of any good species, more or less abortive grains. Sometimes one scarcely finds one good grain; this remarkable fact is shown by the pollen of Cochlearia armoracia, of which I saw never any fruit! although I looked for it since 1851.5

As regards Rhamnus Cathartica I have been rather unfortunate. I have 6 bushes of it in the botanic Garden here, about a week ago in full flower, but all male— I looked them over and over again, but I found no female flower or hermaphrodite upon them—6 Fig 1 represents a mere male flower, which has a quite abortive germen;7 Fig 2 a flower with a germen somewhat better, although not perfect—8 Such germens I found only partly on one bush. No body could tell me here, where I could find a female or hermaphrodite bush— The places about Koenigsberg, in which the plant was formerly plentifull, are all gone; culture has eradicated all the woods in the neighbourhood of the town. I went on the 9th. June with 20 students to the only wood, about 7 engl. miles distant from here, in which I could expect to find Rham. cathart. I explained the object to the students; we searched attentively, but could find no trace of Rhamn. cathart.

That Cytisus has as many other Leguminosae (f. i. Lupinus) short and long stamens, the anthers of which are unequal, in the same flower, you will be aware. As regards the size of the pollen I could find no difference in the two sets of anthers9


Rhamnus cathartica L.

Fig 1 ♂ h.b.rgm. 7.6.186610

DIAG HERE: DAR 111: B45, right-hand one of two

germen tertiam calicis tubis partem aequans. Pistillum omnino abortivum.

Fig 2 Antherae defloratae! Germen abortivum, tamen styli indoles adest.11

DIAG HERE: DAR 111: B45, left-hand one of two

Frutex ♂ h. b. rgm.

Stigmata haud expansa Pistillum tubum calicis fere aequans12

CD annotations

1.1 been … 1851. 2.5] crossed red crayon
2.5 1851.] Line across page after blue crayon
3.1 As regards] opening square bracket red crayon
3.4 Fig. 1 … one bush. 3.6] double scored ink
3.7 The places … anthers 4.3] crossed pencil; ‘I have specimen of Rhamnus’ added pencil 13
Enclosure: expansa] ‘To left’ pencil 14


The date is established by the date of the enclosure, and by Caspary’s remark that he searched for Rhamnus cathartica on 9 June.
Caspary refers to the probable viability, based on external appearance, of pollen in Cytisus adami (now + Laburnocytisus adami).
Now called Laburnum alpinum.
CD reported Caspary’s findings on the percentage of bad pollen in Cytisus species in Variation 1: 388. CD added that such a high proportion of good pollen in the hybrid C. adami was contrary to what usually occurs in hybrids, including those of the same genus, ‘C. purpureo-elongatus’, and C. alpino-laburnum (called ‘C. Watereri’ by Caspary; now Laburnum x watereri, a hybrid of L. alpinum and L. anagyroides). This fact, together with the irregular shape of the ovules in C. adami, was taken by Caspary as evidence that the species was a graft-hybrid. For CD’s interest in graft-hybrids, see the letter to Thomas Rivers, 27 April [1866] and n. 4. Caspary had visited CD on 27 May 1866 (Emma Darwin’s diary (DAR 242)); CD had forwarded flowers of ‘Cytisus purpureo-elongatus’ to Caspary that he had received from Rivers (see letter to Thomas Rivers, 8 June [1866]).
A species commonly known as horseradish.
CD was interested in the different flower forms of Rhamnus cathartica. See letter from W. E. Darwin, [7 May – 11 June 1866] and n. 3.
‘Germen’: ovary (OED).
See Caspary’s sketches. CD and his son William eventually concluded that the species had two male and two female forms, distinguished by the length of their pistils. CD included Caspary’s drawings in Forms of flowers, p. 294, where they are captioned ‘short-styled male’ and ‘long-styled male’.
For CD’s interest in pollen-grains of different sizes in heteromorphic species, see the letter from W. E. Darwin, 8 May [1866] and n. 5.
‘h.b.rgm’ = possibly an abbreviation of ‘hortus botanicus regium’, indicating that the specimen was from the botanic gardens at Königsberg.
‘Ovary one-third as long as calyx tube. Pistil entirely abortive. Anthers withered! Ovary abortive, nevertheless rudimentary style is present.’
‘Shrub’ (see n. 10, above). ‘Stigmas not at all spread out: pistil nearly as long as calyx tube’.
CD had received male flowers of Rhamnus cathartica from William with his letter of [7 May – 11 June 1866].
CD’s annotation refers to the position of the sketch in Forms of flowers, p. 294.


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

OED: The Oxford English dictionary. Being a corrected re-issue with an introduction, supplement and bibliography of a new English dictionary. Edited by James A. H. Murray, et al. 12 vols. and supplement. Oxford: Clarendon Press. 1970. A supplement to the Oxford English dictionary. 4 vols. Edited by R. W. Burchfield. Oxford: Clarendon Press. 1972–86. The Oxford English dictionary. 2d edition. 20 vols. Prepared by J. A. Simpson and E. S. C. Weiner. Oxford: Clarendon Press. 1989. Oxford English dictionary additional series. 3 vols. Edited by John Simpson et al. Oxford: Clarendon Press. 1993–7.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Data on good and bad pollen-grain yields of different species. Sends sketches of two male Rhamnus catharticus flowers [see Forms of flowers, p. 294].

Letter details

Letter no.
Johann Xaver Robert (Robert) Caspary
Charles Robert Darwin
Sent from
Source of text
DAR 109: A81; DAR 111: B45, B48b, B48c
Physical description
inc †, encl †

Please cite as

Darwin Correspondence Project, “Letter no. 10344,” accessed on 28 November 2021,

Also published in The Correspondence of Charles Darwin, vol. 14