RECORD: Darwin, C. R. [1878].07.10-18. Thalia. CUL-DAR209.13.2-11. 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).


Fertilisation Thalia {Look to minute structure of nectaries

July 10th The 2 nectaries not of exactly same shape — longer & more tapering one. perhaps alone secretes—

Enfolding petal much strengthened by adhesion to other lower petals at base.—

Touched tip of another nectary exploded— when not looking fell jar. — a minute drop of n. acid on petal enfolding pistil caused explosion— As did drop on lower nectary, I believe, but I may have touched it.

Is upper short nectary sensitive??

Pods setting self-fertilised.— no insect in Hot-House

Try touching curtain

Try hot water, dropping in after cold — 100°F.

A flower with stalk in n. of Cobalt exploded spontaneously

Hydrocyanic acid rendered flower torpid but limpid so that I dissected it, & the pistil only just began to curve, as figured


10th Within the stigmatic covering I fd. pollen-grains with long pollen tube, full of granular matter— At the distal end of pollen receptacles- many grains were embedded in the pulpy matter, but I saw no pollen-tubes emitted— nevertheless I am far from maintaining it is not a stigmatic surface.—

The lower nectary is longer & its extremity of much paler colour & cells so fine as difficult to be seen— I think fine aggregation

No granular matter in shape one cells all filled with purple fluid

N. B the fringed top of enfolding petal, curving pale certainly is not sensitive, whatever base may be.


Could I pull away enfolding Petal without disturbing nectary much; if so it wd show that the petal does not hold pistil — if pistil explodes will aid in showing that it does keep pistil in place.— first cut away petal in front, where point of nectaries rest.—

If I can free another enfolding petal see if pistil is rigid— & try pricking base of petal or cutting it & cutting free the nectaria

Fibro-vascular tissue in filaments?


July 11' old flower certainly go off spontaneously after a few days

The petaloid expansion of the stamen protects anther fr rain—

Cutting thus the external perianth— the labellum does not cause movement—

The enfolding petal protects beautifully the receptacle with pollen & stigma— Pulling the fringed summit this generally back explodes pistil pollen (as did apparently burning with n. a. but I do not know how far this ran down) but then I distinctly saw that the 2 nectaries were drawn back & of course rubbed against side of great shield petal which faces labellum.

I can see no great difference between 2 front nectaries: lower one thinner, more tapering & pointed, paler & cells rather smaller?

The upper & shorter one forked.

(Another spec. The petals are so folded that with curtain guide insect in inviting proboscis towards the 2 filaments which I suppose are nectaries, as I have often seen drops of nectar round them.— I rubbed curtain repeatedly with bristle— cut away the petal bearing an anther — also cut right down & clean clean away (taking care care not to press against the filaments)


Cu If curtain sensitive bees wd set off pistil too soon, as proboscis must be inserted

Filaments quite flexible—


the largest stiff shield like petal opposite labellum (which also was cut away) & pistil did not go off; but when I pulled back the enfolding petal it went off: This looks as if this petal merely held the pistil, but I tried the strength of pistil after it had become spiral & quite impossible that it shd hold it in such a state of tension: but Dionæa shows that after movement how tension & stiffness suddenly increases.— This pistil is bent a little obliquely to one side in direction of enfolding petal, as I cd see when I had dissected all base. It is beautiful how fringed summit of the enfolded protect the pollen in receptacle & the stigma.—

As sensitiveness must be transmitted through base of enfolder rubbing odd when this is bent setting off pistil.


July 11. Flower put to stand in wet sand in Kitchen

I think long tapering filament had secreted minute minute drop at apex— if so upper one wd be touched at apex by Bee visiting flower—

I see the base of enfolding petal are close to where nectaries arose & one of nectaries corroded by the n. acid

— Pistil not properly curled (after the n. acid) or has subsequently straightened itself. The so called nectaries are flattened & consist of great prolongation of points of petal with fibro vascular bundle running into each — 2 other showed trace of fork & in one of these 2 fibro-vascular bundles entered. The shorter & upper one often seem to contain more granular matter.—

All that I can say is that the 2 filaments often present a different appearance under microscope in dullness of colour & in more granular matter in shorter one & cells more full of cell-sap in longer one.—


July 11


found on roof of stigmatic cavity of flower of which pistil had spontaneously sprung— some many pollen-grains with tubes beautifully developed & deeply penetrating stigmatic tissue.

In the receptacle there was layer of grain. embedded in soft sticky tissue or matter & not one of them & I examined scores with high power had developed tube.— It is not surprising that there shd be self-fertilisation effected by violent movement of pistil, for finest knife-edge separates mass of pollen in receptacle from the lower surface which is truly stigmatic.— upper pulpy surface snow white & looks like stigma— Pollen-grain larger far too numerus for mere self-fertilisation.—

(Examined 2 more nectaries— only safe difference is paler colour greater length & much more tapering form of lower one— so points touch 2 places. — I found 1 pair in which upper was not 1/2 length of lower one.



July 12' a flower with nectaria exposed in Kitchen with stalk in wet sand had large drop of nectar on tip of longer & lower nectary but the shorter one absolutely dry— Perhaps so on another spec. Very good

Pistil much flattened or ribbon-shaped

(From looking to old exploded flower, I conclude that after pistil has sprung pollen-receptacle stand vertical facing great shield like surrounding petal. (probably formed of 3 modified stamen) & upper edge of stigmatic cavity now forms beautiful edge for scraping pollen off bristle or proboscis, & curtain depends vertical between folds of wound pistil.

(Homology. 3 small sepals— 3 larger colored scale-like petals & probably 6 petal-like stamina all confluent at base, but (1) labellum— (2) stamen (3) enfolding petal, the more less confluent, the other forming almost completely confluent & surrounding larger part of flower & stiff apparently serving to keep pistil within flower after its explosion— once I found one which had burst out laterally.


3 Petals scale-like but coloured there important

6 (Bis


July 13th

I doubt whether the so-called nectaria secrete. for I saw great drop on side of petal beneath them.—

(A petaliform purple fold for shield petal aids the enfolding petal in protecting pollen & stigma.)

I cut away petals, labellum & stamen, & found base of pistil closely enfolded by "enfolding petal", which wd prevent it moving in this direction, but it moves in opposite direction.— Again the "fold for the shield" seem opposed to the movement which it tends to takes, but I pulled this clear away & pistil did not move. The sole obstacle to movement is the little catch at base of so-called nectary, but this is only partially opposed to course which it takes, & I believe it serves solely to keep enfolding petal close enfolded.— I have just tried & the little white clasp & whole petal are so thin & flexible it is impossible that they can resist even a very slight force.

I then tried to cut slowly & very gently the enfolding petal but as soon as I made 2d little cut off went pistil, stigma facing side opposite to nectaries. — so this petal is sensitive.—



12th The pistil after exploding sometimes faces are quite round & faces the tips of nectaries, sometime in another position.—

(7 Bis

July 13th At last I have fd. a torpid one— no touching antenna with Bristle caused exploding, but whilst cutting off petals, slowly exploded— 2 or 3 more upper nectaries distinctly forked or with rudiment — Drop Drop of nectar never seems near thin tips, but below them on side of st petal. Pistil whilst enfolded moderately rigid.—

(I have fd. another torpid spec. & punching 2 nectaries with bristle caused it to explode, but when I cut through base of enfolding petal it exploded well.—

(Another was so sensitive that jar from doubling back labellum, caused explosion, I have never seen such a case as this before.)

I have seen several more notched upper nectary & one a rather broad strip of petal with equal, serrated notch at end.— I believe nectar is secreted at base of enfolding petal.

George drawing so truly that distal end of pollen-receptacle is raised up into a convex white hood (upper surface of which is viscid) & formed of this membrane— lower surfaces certainly stigmatic & more arched

Knife edge separates the 2 surfaces.



July 14th The fl buds are dropping off & plant failing & this accounts for not so sensitive.— Had to touch sensitive filament 2 or 3 times. & then exploded carrying round bristle to opposite side of flower. This inevitable as end of pistil presses against rigid "shield petal" & covered bristle with pollen, which stood close to in front of receptacle of pollen— I can now see importance of thickness & rigidity of shield, for on splitting it, it , opened rather widely owing to outward pressure of coiled pistil, which cd not assume proper position & could not sweep round proboscis if it yielded to force of coiling pistil — The curtain & mouth of stigmatic chamber at first horizontal, but after coiling some way became oblique & in this position wd strike with mouth of stigmatic chamber the proboscis already coated with pollen, which will get on as the end of pistil sweeps round the shield— Drop of nectar again at base of sensitive filaments & at base of enfolding petal — spreading some way towards tips of filaments.


14' Another spec. no irritation of filaments caused explosion, but when with needle I pushed the little clasp at base of upper filament exploded. I now find there is a fold in shield petal on side opposite to filaments, & the end of stigma sweep round the shield & is lodged in this fold or cavity— Dotted lines show course of end of pistil. [sketch]

(14th another flower exploded in braking back labellum)

Another flower when I touched filament did not explode, but when I tapped the end of lower filament with very fine & long bristle, exploded (so very little force) used) & I am certain that I tapped nothing but end of lower filaments— lots of nectar at base of filaments, which had spread half way along them. upper filament very short.— The bristle being held long was carried into centre of fold & much adhesive pollen clung to bristle above the receptacle, for the end of pistil in coiling sinks, downwards & therefore leaves pollen above the place where it first touches— The receptacle pushes the bristle before it, sliding downwards at the


same time, thus leaving the adherent pollen above, so that the bee in withdrawing its proboscis will not rub-off disturb the pollen; but when it visits a flower the mouth of the stigmatic cavity will first strike the upper part of proboscis coated with pollen— All is wonderfully beautiful & admirably adapted.

The sketch at back shows position of parts seen from vertically above — Labellum is formed of exterior staminoid.— Stamen probably a petal a staminoid & stamen, united for some way to stamen— Enfolding petal — separate — shield formed by fusion.

(1) Labellum

(2) Enfolding Petal

(3) & 4) Stamen & Petal

5 6} Shield.

(Specimen preserved in spirits for George) from opened flower & seen vertically above.

(In the split open flower, the fold which stops pistil, has end of pistil pinned close to it, & by this fold is the crest, which aids enfolding petal in protecting pollen & stigma.—


The pistil in coiling contract, so as to lie nearly at base of flower, & the end end bends so that the curtain which was horizontal now afterwards directed vertically downwards

؟؟ The spire is a single nearly complete one— one turn of a spire

(July 15th stream of cold water 65° & warm water 119°F produced no effect, but then sensitive filament not sensitive to Bristle. — when I touched or prized up (for I know not which the "white clasp" the pistil went off.—

I have now cut open another fl. of which filaments not sensitive & with bent needle touched the "white clasp", pressing it light in direct opposition to course of pistil, so that I certainly did not free it or pull it off & yet pistil exploded — is very sensitive & nectar lies abundantly all round it.

Another fl. filaments not sensitive— cut open touched white clasp, & rubbed & pricked purple membrane at base of upper filament & at last exploded, but I am not sure whether by pricking I did not prize up the membrane a little.



15' another fl. filaments, not sensitive — pricked purple membranes above base of upper filament, exploded; but it is impossible to prick without lifting up a little the clasp.— One thing is certain that if clasp does hold pistil— its rigidity increases enormously the instant after coiling into spire., for it is excessively rigid whereas the enfolding petal is quite flexible towards base — The little clasp is rather rigid & I believe it is which makes the clicking noise, for I could make such by lifting it up with needle.


Flower of Thalia viewed from vertically above preserved in spirits.

[annotated sketch]

enfolding petal seen from vertically above

great shield petal

fold in shield which arrest stigma with bristle

another with petal united drawn from flower

labellum drawn back from flower


15th Labellum faces 1 of outer sepals.— The enfolding petal & stamen belong to inner whorl— The "shield" consist of 2 perfectly confluent staminoids of outer whorl.

Anthers do no no doubt discharge into receptacle as in Canna— Pistil flattened in plane of curtain— The white convexity at end of receptacle thickly coated with pulpy matter— During explosion much pollen gets forced into the stigmatic cavity & left round sides of shield

I can see no rudiment of 3d inner staminoid.

(July 16' exposed fl. for 2° 30' to 30 minims of S. Ether was fd exploded— Possibly due to excitement, but quite as likely to flaccidity of petals, for the pistil was slightly flaccid.)


I have now looked under compound M. the vessels going to upper filament are just cut through see under Compound

I can see no difference in structure in the clasp, only absence of colour. {see to structure of clasp after spirits.

The fibro-vascular bundle cannot be traced to apex of filaments— These 2 bundles are the most exterior ones. The upper filament of a flower showed no trace of notch, & the fibro vascular bundle was double of thickness of other until near base of filament & than abruptly became thinner: no doubt aboriginally upper filament always forked with 2 bundles.


16' After hot day one went off with shock of gathering— with needle made many longitudinal slits at base of enfolding Petal with no effect, but when I cut fibro-vascular bundle from filament, exploded— the very {slight back-ward pull wd have kept clasp closer.— must be sensitiveness.— I made so many longitudinal slits that base weakened to nothing. I cd see pistil through hole —

{Clasp secretes (in young flower opened to day) large drop of yellowish sweep nectar — extreme surface a caudate & spreads along filaments

(Another fl. cut away shield, so cd see pistil & very gently pricked or bored it some way behind clasp & it exploded— I used hardly any force & if pistil had been pushed back enfolding petal & clasp wd have ben pushed back.)

(Flowers purple produced in long succession, but in hot weather wither after exploding in under 24°— rather small about 1/2 inch in height with ovarium & .4 of inch in breadth — borne on extraordinary peduncles several feet in height & thus rendered conspicuous in native swamps.)


July 17' opened a flower-bud with anther under fringed end of enfolding petal, with pollen ready to come out by slight pressure.— & white highly convex surface at distal very soft & ready to exclude or break up into pulp.— Pistil not sensitive— Curtain dependent— pistil streaked with purple.—

(18th cleared the base of enfolding petal with all connection with stamens. but when I cut the fibro vascular edge, on further side from sensitive filaments pistil exploded.—

(Exposed fl to some drops of Chloroform under small-bell-glass— for 40' (not all evaporated at end) exploded— petals & pistil flexible & flaccid.)

This document has been accessed 900 times

Return to homepage

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

File last updated 26 August, 2023