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Darwin Correspondence Project

From Emanuel Bonavia   [before 7 September 1868]1

Regarding peloric forms of flowers, I have observed an instance which appears unrecorded in the Clitoria Ternatea. I send you herewith two imperfect coloured drawings, made by a native artist, to illustrate the striking difference between the irregular and peloric form.2 The Clitoria Ternatea is a scandent twining plant, with solitary flowers in the axils of the leaves. As you know, the vexillum, contrary to most pea-shaped flowers, is lowermost. No. 1 shows the irregular form. It presents the following characters:—Segment of calyx corresponding to the carina longest, vexillum large, emarginate, having in its middle part a yellowish white patch, with veins pinnately disposed, its margins meet round the alæ and carina; alæ small, with recurved blue margins adhering to the carina; carina white, completely enclosed by the alæ; stamens ten, diadelphous.3 In the fully developed peloric flower of the Clitoria Ternatea the alæ, carinæ, and vexillum are of equal size; they all have that middle yellowish white patch which, in the irregular form, is found only in the vexillum. Some flowers are so beautifully peloric that there is no distinguishing which petal represents the vexillum. I made a section with a knife through all the petals of one of these forms. This section shows well the twisted disposition of the petals, each of which is overlapped by the edge of the next petal. The stamens are ten, and all free and regularly disposed. This peloric form is transmitted by seed. Different forms of Clitoria graduate from the ordinary irregular shape up to the perfectly peloric flower. Different degrees of pelorism are found as a rule on different plants, but many degrees are often found on the same plant. I have observed six well marked degrees:—

A. Natural. Alæ small, edges recurved, and completely hiding the carina; one stamen free, nine united. This form I have always seen by itself on a plant. No peloric ones on same plant.

B. One of the alæ larger than the other, more expanded, allowing the carina (which is a little larger than usual) to be visible; three stamens free, seven united.

C. Alæ much developed, and only one of the petals of the carina largely developed; two stamens united, eight free.

D. Alæ almost as large as the vexillum, but still occupying the place of the alæ; petals of carina both much developed, but still somewhat enclosed by the alæ; all stamens free.

E. All the five petals are equal in size and similarly marked, but in æstivation the vexillum is still the outermost petal: the other four petals have a somewhat twisted disposition, totally different from that of alæ and carinæ; all stamens free. The plants which bear this form also bear some flowers, which are

F. Perfectly peloric, and in which (all stamens free, and regularly disposed) neither vexillum, alæ, or carinæ are distinguishable. One edge of each petal is free, while the other is overlapped by the free edge of the petal next to it.

I have seen several specimens with four petals only, of equal size, and with eight stamens. I have white varieties of this Clitoria, which are also peloric.


The date is established by the relationship between this letter and the letter from M. T. Masters, 7 September 1868.
Clitoria ternatea, a tropical plant in the family Leguminosae, is known as the butterfly pea, blue pea, or blue vine (see Mabberley 1997). Leguminous flowers are normally bilaterally symmetrical; peloric forms are abnormal variants displaying radial symmetry. CD discussed other peloric plants, including his experiments on Antirrhinum (the snapdragon), in Variation 2: 58–60, 345–6. See also Correspondence vols. 11–14. Bonavia observed C. ternata in Lucknow, where he was the civil surgeon with the Bengal Medical Service (Oldenburg 1984, p. 97, Darmanin 1998). The drawings have not been found.
In leguminous flowers, the vexillum or standard is the largest, and usually the uppermost, petal, and encloses the others; the alae are the side petals; and the carina consists of the two lower and usually smallest petals (see A. Gray 1857a). The drawings were not reproduced in the Gardeners’ Chronicle, where this excerpt from Bonavia’s letter was published.


Peloric forms of flowers: Clitoria Ternatea.

Letter details

Letter no.
Emanuel Bonavia
Charles Robert Darwin
Source of text
Gardeners’ Chronicle and Agricultural Gazette, 26 September 1868, p. 1013

Please cite as

Darwin Correspondence Project, “Letter no. 6352F,” accessed on 19 July 2019,

Also published in The Correspondence of Charles Darwin, vol. 16