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Darwin Correspondence Project

From J. D. Hooker   [early December 1856]1

Dear Darwin

A M. Tulasne has published lately a splendid monograph of Podostemaceæ & says that some species certainly fecundate under water, though others may not do so & some caulescent ones raise their flower stems above water to flower.2

My species were gathered at the end of the rainy season when the streams were very swollen, they grew appressed like Lichens to rocks, only under water & only away from the rocks of the bank, they were covered with minute flowers that are almost sessile—& grow in the most rapid water.

No species grow in the Himalayan rivers, which I consider very curious & suppose to be owing to the great vicissitudes of their temperature. They are found in the Khasia, Mountains of the Peninsula & Ceylon besides America, Madagascar & various other countries. (see Himal. Journals. II. 314 for footnote.)3

Furthermore some species actually cover the whole bottoms of the streams that are never dry & these flower & fruit abundantly

In Kerguelens Land I most particularly attended to Limosella flowering in 2 feet water; with a bubble of air in each corolla & I assume it is the same thing with Podostemon but I have a bottle full in spirits & will examine.

I do not see why the occasional partial drying of a stream might not let some flowers of Podostemon be exposed & be left for you to cross by any means you chuse.4

Ever Yrs | Jos D Hooker

Footnotes

The letter is dated by its relationship to the letter to J. D. Hooker, [early December 1856]. It seems to supplement the information given by Hooker in his notes written on the letter (see letter to Hooker, [early December 1856], n. 5) and may have been sent to CD at the same time.
J. D. Hooker 1854, 2: 314 n. The passage is marked in CD’s copy, now in the Darwin Library–CUL.
CD repeated this point in Natural selection, p. 63: ‘Dr. Hooker has never seen them flowering in the open air; but he will not assert that this may not sometimes occur, when the torrents sink.’

Bibliography

Natural selection: Charles Darwin’s Natural selection: being the second part of his big species book written from 1856 to 1858. Edited by R. C. Stauffer. Cambridge: Cambridge University Press. 1975.

Tulasne, Louis René. 1852. Monographia Podostemacearum. Paris.

Summary

Podostemaceae flowering under water.

Letter details

Letter no.
DCP-LETT-1966
From
Joseph Dalton Hooker
To
Charles Robert Darwin
Sent from
unstated
Source of text
DAR 100: 149
Physical description
2pp

Please cite as

Darwin Correspondence Project, “Letter no. 1966,” accessed on 20 January 2020, https://www.darwinproject.ac.uk/letter/DCP-LETT-1966.xml

Also published in The Correspondence of Charles Darwin, vol. 6

letter