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July 1878

Trifolium subterraneum Circumnutation of Flowers

Stem or shoot tied close to base of Peduncle

July 23d-24th A young flower-Head stood vertical up & thin straw with marks affixed to upper end of peduncle no it was fixed to side of & to one of flowers & not to summit of the peduncle so as to stand upright.

Tracing used for circumnutation of flower-peduncles

Observed under skylight, moderately warm day Temp.

Traced on Horizontal roof under skylight — Tracing more Tracing much magnified See Tracing I, shows that the peduncle alone of young flower-head circumnutates plainly

[in margin:] See Back for Sketch.

Frank mark side at 8°. 40' say 50 a.m July 23

By 10° 30' P.m on 24th had begun to decline towards me.

(on July 25'' 6° 45' 7°— after 46° a.m, the straw stood a little above horizontal, 19° above Horizon. 71° for the whole & a new tracing began on temporary vertical glass. (see Tracing II.) The peduncle & flower now rose a little till 6° P.m; fell during night & rose next morning (26th), but fell again lower than ever. During morning of 27th. But either owing to condition or to flower not having been fertilized, the peduncle never fell after falling beneath [the] horizontal position & the line, bent upwards, especially the extreme end, to which end of straw attached (!) turned a little upwards (!); so we learn from these observations only that the peduncle bowed down rapidly to a horizontal position & then circumnutated much; & afterwards from some cause did not behave normally.—

At the commencement we clearly see that the bowing down is modified circumnutation

(Jun 22d 1879 N. B flower-head quite young — perhaps failed to fertilise itself, & probably would after a long time have bowed vertically down??

[226v]

Horizontal glass [sketch] 23d

 

(4 Ellipses, modified by [illeg] in one direction between 8° 40' a.m 23d & 9° P.m 24' ie in about 36°. —)

[sketch] on the 25 Vertical glass

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Trifolium subterraneum

Tracing III

An old flower-head, well naturally bowed vertically down & 1/2 inch above sand with stem secured at base of peduncle was observed from 9° 30' am. to 7° 15' P.m on July 24th (see Tracing III.)— made 2 little circles.

[sketch] Horizontal glass shoot

[sketch] sand

We learn from this that old flower-peduncle goes on circumnutating before it touches Earth.

On July 25'' at 9° 15' a.m shoot was cut free & flower had instantly sunk about 1/2 inch & rested on sand, & tracing then continued, See from 9° 15' a.m on 25th to 8° a.m on 26''. During this time plainly circumnutated & made a figure, which represents at least four circles in 23h.— Whilst thus circumnutating during 23 hr the flower-head buried its apex in the sand. There can, I think, be no doubt that the movement is very important for this end, considering the extreme lightness of flower-head with peduncle & end of shoot, from which the peduncle sprung. —

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Trifolium subterraneum

First Flower

An old flower-Head bowed somewhat down with shoot not tied with glass filament & bead on end fixed transversely across peduncle & movement traced on roof under skylight, from July 22d 4°. 35' P.m., to 6° 45' a.m. July 25th [sketch]

N. B. This flower-Head had buried itself in 6° for white sand had been put on soil at 9° a.m & by 3° it had partially buried itself obliquely in a little heap of sand. Tracing IV relates to movements after this partial burying. The bead moved chiefly in one direction but in very zig-zag line: from 10° 40' P.m on 23d it quite changed its course & travelled at right angle to former course in very zig-zag line & clearly circumnutated but on very small scale. This movement must aid in burying itself, for shoot bearing peduncle itself long loose long & flexible.

N.B shoot peduncle increases greatly in length in bowing downwards.

(on July 26'' movement again traced from 8° a.m to 9° a.m. 27'' & was clearly circumnutating — see Tracing IV.A — The flower-head now buried in little sand-heap, except tips of long bracteæ calyces of flower-head)

(on July 29th 29' Even the tips of calyces now completely buried; so made another tracing during 11° 15' from 8° a.m to 7° 15' P.m. (see Tracing IV B & the flower peduncle was still circumnutating — I think little no doubt movement aids in burying it — for peduncle not very stiff & long & shoots flexible

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Trifolium subterraneum

A Peduncle with flowers just withered was extended 36° below horizon, stem tied close to base, & filament with sight affixed transversely across the peduncle close to Head, & another filament across middle of peduncle Tracing. [sketch]

July 22d First for filament close to Head, See Tracing V. observed on 22d from 11° a.m. to 11° P.m. & during this time moved 4 times obliquely down & 3 times up, & so was clearly circumnutating.

Was Observed once each day till 27th & continued to fall, always circumnutating though less, & fell during three days vertically down quite as much as rather more than the height of diagram length of Tracing; but the attachment of filament, or the obscure light somewhat interfered with ultimate movement & peduncle did not descend become so so much curved downwards as flowers in on plant in open air.

With respect to filament attached to middle of peduncle the movement here was not so great, & what is remarkable the movement did not coincide with that close to the Head, for on one occasion, the upper filament was moving up while head was moving down.

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Trifolium subterraneum

[in margin:] See Back rough Tracing

A flower-head standing vertically up, with stem tied at its base had filament attached to it & observed on roof of case from 11° on July 22d to 5° P.m & during these 6° moved from the roof to vertical side. The line was chiefly straight but with one well-marked zigzag. By 7° am on July 23d was bent almost vertically down, so in 20° had passed through not far short at 180°— The stick (to which shoot at base of peduncle was tied) was now ie at 8° a.m. 23d raised much up, so that shoot peduncle now stood only between 10° & 20° below horizon; but by 11° had sunk so much cd hardly be traced, but the peduncle never sank much more so as came to face more stand at more than right angle with the upwardly raised shoot & the flowers stood at right angles to peduncle instead of being pressed back against them

These observations show how quickly the peduncles under favourable circumstances bow downwards.