RECORD: Darwin, C. R. [1878].07.18-20. Calathea / Thalia. CUL-DAR209.13.12-13. Edited by John van Wyhe (Darwin Online,

REVISION HISTORY: Transcribed by Christine Chua and edited by John van Wyhe 7.2023. RN1

NOTE: See record in the Darwin Online manuscript catalogue, enter its Identifier here. Reproduced with permission of the Syndics of Cambridge University Library and William Huxley Darwin. The volume CUL-DAR209.13 contains materials on fertilisation (Thalia) for Darwin's book Movement in plants (1880).


These flowers stand in pairs with right-Hand & left-Hand projections

July 18th Calathea longibracteata flower sent from Kew— touching folded filament with hair or bristle does not start it, or deeply pricking pistil, but a very slight push outwards (as insects wd do) of the filament frees the pistil & so I have no doubt that it is the action is purely mechanical, & if so it is probably the case with Thalia—

Maranta Luschnathiana behaves, I believe, in same way.—

(If first flower open of Calathea, try again— with hairs— or acid — or chloroform drips of.

Case like Isotoma

Minute Drop of N. Acid did not cause explosion; but do of Chloroform did do so— but as filament is folded up into tube, it seemed to draw the fluid to base of petal & chloroform causes petals to curl & this wd free clasp.—



I tried repeatedly with Right & Left-Hand flowers (for some have filament on right & some on left) in some respects parallel case to that of Thalia) & the filament on spur which is stiffish can be bent towards centre of flowers & which keep clasp on pistil, without exploding, but in the least bend in opposite direction causes explosion.—

If hole drilled gently low down pistil, it is such a state of tension that it breaks itself & the upper part curls upwards without freeing itself from hood— everything shows mere mechanical action.— Repeated experiment with same result.

Fibro-vascular bundle in folded filament

Enfolding petal not so stiff as I shd have expected — though rather more so than in Thalia.— Pistil most curious in rigidity like Dionæa after exploding; for it is here very stiff though not so stiff as in Thalia


19th July


I cut away part of shield & pressed with cut-off-head of fine ent. Pin on the shield, & it exploded after doing so once or twice.— I cannot conceive that I could have pulled shield away— Moreover sensitive filaments are generally pushed against wall of flower & if they were to act as levers they must be pushed still furth in same direction.

I touched clasp of another fl. repeatedly before it exploded with point of needle pressing on it— at last it exploded— I think I could not have pressed it at all from the pistil so as to have caused it to slip off.—

In another fl. I bored the sensitive filaments & smashed the tips with pincers & pistil did not explode, but when I touched clasp off it went.—

In another flower, I touched the clasp. with cut-off square end of fine ent. pin, in such a direction, that I believe I


I believe I could not in the least have pushed off clasp, yet it instantly exploded— young flower with great drop of nectar about the clasp. — The strongest argument is the position of filaments, so that insects cannot push them in f manner to with draw clasp.—

July 20th 8°. 30' a.m To day in turning back one of true petals exploded— also its other flower, after cutting shield in turning it back— This flower was not open at 4° P.m yesterday.— Seeing how insensible the sensitive filaments have lately been & how easily the pistil explodes all spontaneously or by slightest jar— may not the late flowers have become more adapted for self-fertilisation, when probably less visited by insects.—

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Citation: John van Wyhe, ed. 2002-. The Complete Work of Charles Darwin Online. (

File last updated 26 August, 2023