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Translation of Linnaei
Somnus plantarum

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p 338 /10. Many will think, perhaps, that the nocturnal change in plants which we call sleep is simply the effect of cold making the leaves rigid. We see this in the way some tender plants seem as it were to shelter themselves with their leaves in autumn - specially Euphorbia Lathyris, Ocymo fruticoso, beymous fruticoso, Asclepiade curassavica, Solano fruticosum & bahamensi, the leaves of all of which cling to the stem in the cold, the Solanum Bahamense in a very remarkable manner, most of the leaves so twisting themselves as to invert the inner & outer surface, but those towards the South keeping their natural attitude, when the sun is warm.

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/11 but it is enough to disprove this exclusive ascribing of the sleep of plants to chill, that it takes place at the stated time even in a hot room, & all the same whether the windows are open or shut, a fact that may be observed any day in the Academic garden. These almost voluntary changes (as they appear) are truly wonderful, & show us with what art plants have been constructed.

/12 it is also to be noted that plants, like animals, take sleep more readily while they are young & tender, & I advise any one who makes experiments on the subject after me to begin in the spring, which I was not

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able to do.

13 the first plant which led me N.D.P to suspect this fact (of plants sleeping) was Lotus ornithopodioides, which was sent by one of the greatest physicians & botanists of our time, Dn de Sauvages. 2 blossoms were open on the plant, of N.D.P intended to give the gardener particular orders to be careful of it, but being interrupted by some business he did not give the direction till evening, when he called the gardener to show him the plant, but they looked for the blossoms in vain. The same thing happened on the following evening, in spite of the most diligent search of both of them & so convinced was the gardener of their absence

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That when he found them on the following morning he insisted that they must be newly come out. On the evening of this day, however they did after a very careful search find the two flowers [Darwin annotation: "Bratiae?"] hidden under 3 leaves. This phenomenon led N D P to make observations & experiments which convinced him that the same drama was played throughout the whole vegetable Kingdom.

(I cannot make out who this N.D. is, P is for Preeses I suppose, & a former mention makes him President Preeses in Philosophic Botany.)

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P 340. /14. The leaves of plants are either simple or composite; it is the latter which more especially sleep as they are extremely well fitted to contract themselves whence we may discern that the structure of leaves is not accidental, but destined by the omniscient Creator for a fixed end. Simple leaves however, are seen to vary their position in this sleep in the four following ways.

1st [Darwin annotation: "341 Simple Leaves"]

In closing (connivendo) when 2 opposite leaves apply themselves so closely to each other by the upper surface as to appear but one, the

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tender [Darwin annotation: "buds of the [illeg] branches &"] of the leaves & fructification being sheltered under this envelope from the nocturnal air

2. By shutting in (incluendo) when the alternate leaves approach the stem at night, so that the tender stem or blossom is safely hidden between the stem & the leaf [Darwin annotation: "(Tobacco)"]

3 by and encircling (circumsesiendo) of the leaves, which at other times are horizontal at night rise erect, & surround the stem, or the apex of the little shoot, forming a funnel under which the tender flowers & budding leaves are kept safe & sound

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4. By sheltering (muniendo) when the topmost leaves with their long stocks, which were previously spread out horizontally, hang down & form as it were a vault, in which neither wind, dew, nor rain nor any other external injury, can reach the tender leaves, nor flowers.

[Darwin annotation: "P.341"]

(Composite) leaves defend the tender shoot in 6 manners viz.

1 By embracing (conduplicando) when the leaflets mutually approach each other, covering their upper surface like the leaves of a book.

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2 By involution (involvendo) when the leaflets only close at their points, thus forming a cavity whence the tender blossom may lie hid

3 by divergence [Darwin annotation: " I suppose move upwards"] (divergendo) when they approach only at their base, the points spreading open

4 by hanging down (dependeudo) so that the dew of rain do not spoil the shoot, nor the wind shake it

5 by inversion (invertendo) [Darwin annotation: "& imbricado"]

6 by taking the shape of a fluted tile imbricando [Darwin annotation: "Intricated"] so that in both cases

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the more tender surface of the leaf may be covered & the foot-stalks themselves sheltered.

(P 342 has a general plan of these classes. Then follow examples)

Conniventia

[Darwin annotation: "Simple leaves, opposite"]

The Atriplex hortensis closes every night with its uppermost leaves till the time of florescence, shutting in the tender shoot between the topmost pair. [Darwin annotation: "Simple leaves"]

2. The Asclepiades, of different species, erect their leaves through the night

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of the two uppermost unite closely so as to conceal the tender blossoms.

The Alsine brings together a pair of leaves above the stalks in the middle of the night, so as to shut in the first beginning of the shoot, & when the topmost pair but one can boast of longer stalk this closes over the topmost & shuts in the nascent shoot.

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Includentia [Darwin annotation: "Simple leaves"]

The Sidea Abutilon erect at night, their upper leaves (one of which is larger than the other) on their stalks so that they may better approach each other, but the leaf itself, which by day spreads open, hangs perpendicularly down, so that the upper surface is turned outwards in a vertical direction of the lower surface fitted closely to the other leaf, so as to compress the sprouting shoot between them

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8 [Darwin annotation: "Ayenia"]

The Ayenia follows exactly the same procedure

The Oenthera Mollisima raises, at night, its horizontally spreading leaves, so that before the flower is properly open they are perpendicular closely compressing it between themselves & the stem keeping it safely guarded, but when the fecundation is effected this is not observed to take place any more

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Circumseptientia [Darwin annotation: "Simple leaves"]

[Darwin marginal annotation: "Seems to act for protection of flowers"]

The Peruvian mallow [Darwin annotation: "Malva Peruviana"] bears lobed spreading leaves fixed on longish stalks, & from the axes wings of the leaves a unilateral spike with flowers covering the upper side of the erect peduncle, but when night comes on [Darwin annotation: "flower"] peduncle curves downwards while the leaf-stalk raises itself & embraces with the leaf, like a hand, the bent spike, so that the flowers lie hid in the bosom of the leaf the whole night, safe from

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all injuries from the air, an astounding providence of nature.

8. L The Iva Annua raises at night its leaves, before open, into the shape of a funnel, under the protection of which the tender plant is protected from injury, lest it might be hurt where it is about to produce its most noble part.

9. The Parthenium Hysterophorus shows its relation to the foregoing during sleep, in spite of the difference resulting from

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the frequent division of its leaves, raising its topmost leaves in the same manner & enclosing within them the tender plant

10 The Mandragora opens its leaves by day, that the flowers may be open, but by night it raises its leaves that the flowers may not be visible.

11 The Datura Stramonium raises at night its open leaves, specially the topmost ones, that they may surround the fructification on all sides

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12. Amaranthus tricolor. The leaves surround the summit of the stem at night so as to defend it both above & at the side.

13. Amaranthus cruentus [Darwin annotation: "cruentus"] raises its leaves more than any other kind of Amaranthus

14 The Celosia cristata [Darwin annotation: "Celosia"] sleeps in the same way as the Amaranthus, only that is has not so many leaves at the top of the stem.

15. The Bidentes raise their opposite leaves at night

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4. Munientia

16. The Hibiscus Sabdarissa [Darwin annotation: "Sabdarissa"] bends back at night the top of the leaf stalks, (which are erect by day) so that the leaf which is horizontal by day by night hangs down like a shield, rigid, not slack. The leaves like so many shields defend the tender stem.

16 The Achyranthes aspera has a peculiar manner of sleeping the topmost leaves, while still tender by night are laid open in the shape of a cross, but by day are again raise upright.

18. Impatiens noli tangere sleeps at night with hanging leaves & loose stalks.

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19. The Sigesbeckia orientalis bends back, at night, its leaves, their stalks being rigid, & forms a vault for the tender germs.

20 The Milleria quinquefolia does just the same

21 The Malvascariosa bends downward, at night, the fully developed leaves, so that they may touch with their points the bough below.

Conduplicantia [Darwin annotation: "Compound Leaves"]

22 The leaves of several Bauhiniae while still tender, turn their two lobes towards each other so that their surfaces touch each other mutually.

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23. Hymemaea Courbaril [Darwin annotation: "Casriae"] has its name from the fact that its two leaflets, while still tender unite themselves through the night so as to look like one leaf.

24 The Lathyrus odorata & many others not only closely compress their leaflets at night but bend their points towards the stem, in a very different position from that taken by day.

25 The Colutea arborea [Darwin annotation: "Trifolium repens"] raises its leaflets so that they approach in pairs, the odd one being erected transversely

(I do not understand what this means but the Latin is clear. I suppose it means that each leaf crosses to meet the one not opposite it. HW.)

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26 The Colutea fruticosa bends its leaflets at night towards the setting sun & makes them more fluted erect against the stem.

27 The Hedysarum coronarium erects every night its common stalks & closes its lateral leaves on to the side that is uppermost the odd one, transverse & erect closes the series.

28 The Psoralia pinnata [Darwin annotation: "Leguminosa[?]"] also erects its common stalks against the stem, & brings together its leaves in pairs.

29 Vicia Faba raises its leaflets every night so that they unite by pairs [Darwin annotation: "Not in Hot-house"]

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Involventia [Darwin annotation: "Compound leaves"]

30 Trifolium resupinatum raises its leaves during sleep & with them presses the head of flowers proceeding from the wings [Darwin annotation: "axes ?"] of the leaf, closely to the stem

31 Trifolium incarnatum follows almost the same procedure as does also

32 Medicago polymorpha.

33 Lotus tetragonolobus turns its footstalks to the stem with bent leaves embracing the shoots & blossoms so as to cover them on all sides

34 Lotus ornitopodioides depresses its boughs of stalks, both erect by day. This plant bears 3 tracts under the flowers, open by day so that the flowers almost rest upon them

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but by night these leaves close over the flower so artificially the odd one forming a roof to the two lateral ones, that the utmost diligence is necessary at night to discover the flowers.

Divergentia [Darwin annotation: "Compound leaves"]

35 Trifolium melilotus polonica, officinalis & caerulea have a peculiar position the odd leaflet, at other times spreading horizontally, fixed itself vertically in such a manner, that one edge looks towards the sky, another towards the earth but the lateral leaves remain unchanged, whence it happens that these leaves are firmer in the air, not being so easily shaken by tempests.

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36 The Trifolium Mel. Italica has almost the same procedure except that the lateral leaves which do, indeed also become vertical, so turn as to change their inner for their outer surface, they are so closely compressed at the base that they must certainly be less agitated by the wind or weighted by the dew

Dependentia [Darwin annotation: "Compound leaves"]

37 Lupinus albus hangs its leaves the other Supiores erect them during sleep

38 The Oxalis incarnata hangs its leaves, the stalk approaching the stem that the tender leaves are covered, as those of the Lupine.

39 Ipomoea aegyptia bends back its leaflets to the peduncle, so

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That they may be said to hang but their particular good stalks are rigid, whence it is evidence that leaves do not hang down from flaccidity but from some other cause, & this is observed to happen in a heated room as well as in the cold open air.

40 Phaseolus semierectus every night erects its footstalk, (even in a warm room) so that it comes nearer the stem to which it becomes almost parallel at the same time hanging its leaves so that 3 external walls are made the stem supplying the fourth, between which the nascent buds are sheltered

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41 The Hedysarum canadense observes the same manner of sleeping.

42. Robinian Pseudo acacia puts down its leaflet joining them by pairs beneath the common stem by their under surface, but the individual footstalks are quite rigid so that these bending is as it were voluntary; the odd leave hangs at right angles. (see plate)

43 Glycyrrhizae sleeps in the same manner, as does also

44 Amorpha fruticosa, & that in a worm room or the open air, &

45 Glysine abrus, but so that the hinder edge of the leaflet always rests on the next

[Darwin annotation: "In this case there can be no protection to bud or footstalk"]

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[Darwin annotation: "Invertentia compound"]

46 Almost all the Cassiae have a wonderful way of sleeping peculiar to themselves, the common stalk being first raised a little then the leaflets bent under it in pairs closing like leaves of a book [Darwin annotation: "No not in by then[?]"]  beneath the stem but what most raises astonishment is that it is the outer surface of the leaflet which become the inner & hidden one, & that by so remarkable a bending that it could hardly be effected by day without tearing the leaflets. (See plate)

Imbricantia

47 The Tamarindus Indica, having simple pinnate leaves, lays the foot stalks together in the shape of a gutter-tile along the common stalk

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So that the lower surface, at night, becomes the upper, thus both the whole stalk & the upper surface of the leaves are sheltered.

48 Haematoxylon.— Same method.

49. Almost all the Mimosae erect at night their partial leaves a little, but unite their own leaves in the shape of a gutter, following the common stalk, so that the lower surface turns outward in such a way that the individual footstalks & upper surface of the leaves are entirely hidden from the dew & cold & the whole plant less exposed to the wind. It is imitated by a Gleditsia 51 see plate

50 Mimosa virgata differs only in this respect, that that common peduncles, but not the partial ones, hang down, the leaflets being overlaid not longitudinally following the footstalk, but a little above them. (See plate)

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I have above given all the different positions in which plants sleep but have not adduced all examples of these various positions lest my work shd be inconveniently large. And since it was my design to show the different attitude of leaves in sleep I have not gone any further, however it has not escaped me that the parts of the fructification themselves often sleep, & though I am unwilling now to enlarge upon this I mention the following instances Euphorbia germanica bends its umbels every night as long as they are in flower so that the anthers are sheltered from dew or rain

So do several others which he specifies

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viz Geranium striatum, Ageratum conyzoides, Ranunculus polyanthemus, & verbascum blattaria

But all these can be better pictured by the eye than the pen. If therefore it does not displeasure L.B will go on summer evenings to the flowers I have named & see for himself these most wonderful natural phenomena, which no one as yet observed by none he will taste a delight, I promise, that feeds the soul of the mind. (P 350

Appendix

Solanum Melongena raises its leaves at night, so that it less touches the disc of the largest leaf, like the Vicia narbonensis

Verbesina nodiflora joins the bases of the leaves in a flat disk, the points being bent back

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Achyranthes lappacea bends its branches at night, like the Lantana

Triumfetta drops its leaves & brings them near the stem

Mimosa chinensis joins its leaves above the partial footstalk like a saw

[Darwin annotations:]

p. 7. Sidea leaf hangs perpendicularly down

15. Lathyrus odoratus !!

16 — Vicia faba

Amaranthus 12

Sigesbeckia 14

Reference:

Linnaeus, Carolus (Carl von Linné). 1759. Somnus plantarum. Handwritten English translation by Hensleigh Wedgwood. (Doctoral dissertation of Peter Petersson Bremer under the supervision of Linnaeus. 22pp.)  In idem. 1749-1790. Amoenitates academicae: seu dissertationes variæ physicæ, medicæ, botanicæ antehac seorsim editæ nunc collectæ et auctæ cum tabulis aeneis. 10 vols. Stockholm: Laurentius Salvius, vol. 4, pp. 333-350.