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Darwin Correspondence Project

To W. E. Darwin   [14–17 May 1864]1


P.S. I begin to think it would be far safer to measure pollen dry . Some time try whether you could not put thin glass over dry scattered pollen & secure thin glass over the slide by 2 little balls of wax as big as pin’s heads.— You must be tired of my requests, otherwise I would send another red Cowslip to be measured dry.—2 The Pulmonaria pollen looks very different size dry.— Look for the shrivelled & small grain in long-styled Pulmonaria in dry state.—3


The date is established by the reference to observing shrivelled and small grains of Pulmonaria angustifolia pollen, as CD had mentioned in his letter of 14 May [1864]; William responded to CD’s request to observe the pollen dry in his letter of 18 May [1864]. See also letter from H. E. Darwin to W. E. Darwin, [18 May 1864].
William had already sketched pollen for CD from the two forms of wild yellow cowslip and from an equal-styled red cowslip (see memorandum from W. E. Darwin, [30 April 1864] and nn. 3 and 4). In his letters to W. E. Darwin of 3 May [1864] and 5 May [1864], CD had asked William to soak the yellow cowslip pollen the longest before measuring it; he included an equal-styled red flower from a new seedling in the second letter.
For CD’s interest in the shrivelled pollen-grains from long-styled Pulmonaria flower-buds, see the letter to W. E. Darwin, 14 May [1864] and n. 6).


Instructions on measuring pollen of dimorphic plants.

Letter details

Letter no.
Charles Robert Darwin
William Erasmus Darwin
Sent from
Source of text
DAR 97: A3
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 4479,” accessed on 16 April 2024,

Also published in The Correspondence of Charles Darwin, vol. 12