To J. D. Hooker 21 October 1
Down, | Beckenham, Kent. | Railway Station | Orpington. S.E.R.
My dear Hooker
Having as a wonder no letters to write, I am going to amuse myself by scribbling a few lines to you.— Perhaps you wd. like to read enclosed on Gunnera: anyhow it need not be returned.2 I wonder whether the same explanation can apply to odd little flower in middle, or on axis of umbel of Carrot, which has always been a mystery to me.3 By the way a Melastoma (I know not what or whence) has just flowered in my hot-house, but the 2 sets of stamens do not differ except in size: I have however fertilised a few flowers with pollen from both.4
The boys have been observing Stipa, & Horace has made a hygrometer with a bit of the twisted awn or pistil (or whatever it may be) & mounted it on a graduated circle; & I have never in my life been more astonished than at its sensitiveness.5 If you blow gently at it from 1 or 2 feet distance, it absorbs moisture & instantly rotates. It is still more surprising that the moisture from a finger held near, not touching, instantly & repeatedly caused a slight movement of about a degree.— What a strong attraction for water the cells must have! We have been disgusted to find in Watts Dict. of Chemistry that some one has used Stipa as a hygrometer.6
I have been nicely sold: I saw in a Journal that Dr Pfeiffer gigantic Nomenclator Botanicus is now published, & I assumed that it was like Steudel’s with a list of the species & Habitats, so ordered it.7 And now I find it costs £12"s12.0 & that it contains no species,, only genera, & is of not the least use to me or to anyone, except a describer. Would it be real use to Linn. Soc? If so I wd give it to the Soc. or to any poor working Botanist, or I will ask William & Norgate whether they could sell it for price.8 It is folly for me to keep such a book.
Ever yours affecty | C. Darwin
Describes observations by his son Horace on the extreme sensitivity of twisted seeds to moisture.
Please cite as
Darwin Correspondence Project, “Letter no. 10209,” accessed on 6 December 2016, http://www.darwinproject.ac.uk/DCP-LETT-10209