Sept. 3, 1874] 



NATURE 



367 



small erect spines are fixed near the midJle of each lobe, among 

 the glands, that efTeetually put an end tn all its struggles. Nor 

 do the lobes ever open again, wliilc the dead animal continues 

 there. But it is nevertheless certain that the plant cannot dis- 

 tinguish an animal from a vegetable or mineral sulistance ; for if 

 we introduce a straw or pin between the lobes, it will grasp it 

 fully as fast as if it was an insect." 



This account, which in its way is scarcely less horrible than 

 the descriptions of those medieval statues which opened to 

 embrace and stab their victims, is substantially correct, but erro- 

 neous in some particulars. I prefer to trace out our knowledge 

 of the facts in historical order, because it is e.xtremcly important 

 to realise in so doing how much our appreciation of tolerably 

 simple matters may be influenced by the prepossessions that 

 occupy our mind. 



We have a striking illustration of this in the statement pub- 

 lished by Linnreus a few years afterwards. All tht facts which 

 I have detailed to you were in his possession ; yet he was evi- 

 dently unable to bring himself to believe that Nature intended 

 the plant — to use Ellis's words — " to receive some nourishment 

 from the animals it seizes ; " and he accordingly declared, that as 

 soon as the insects ceased to struggle, the leaf opened and let 

 them go. He only saw in these wonderful actions an extreme 

 case of sensitiveness in the leaves, which caused them to fold up 

 when irritated, just as the sensitive plant does ; and he conse- 

 quently regarded the capture of the disturbing insect as something 

 merely accidental and of no importance to the plant. lie was, 

 however, too sagacious to accept Ellis's sensational account of 

 the coup de grace which the insects received from the three stiff 

 bail's in the centre of each lobe of the leaf. 



Linnreus's authority overbore criticism, if any were offered ; 

 and his statements about the behaviour of the leaves were faith- 

 fully copied from book to book. 



Broussonet (in 1784) attempted to explain the contraction of 

 the leaves by supposing that the captured insect pricked them, 

 and so let out the fluid which previously kept them turgid and 

 exp.anded. 



Dr. Darwin (1761) was contented to suppose that the Dionnsa 

 surrounded itself with insect traps to prevent depredations upon 

 its flowers. 



Sixty years after Linnx'us wrote, however, an able botanist, 

 the Rev. Dr. Curtis (dead but a few years since) resided at 

 Wilmington, in North Carolina, the head-quarters of this very 

 local plant. In 1834 he published an account of it in the Boston 

 Journal of A^atnral History, which is a model of accurate 

 scientific observation. This is what he said : — "Each half of 

 the leaf is a little concave on the inner side, where arc placed 

 three dehcate hair-like organs, in such an order that an insect 

 can hardly traverse it without interft ring with one of them, when 

 the two sides suddenly collapse and enclose the prey, with a force 

 surpassing an insect's efforts to escape. The fringe of hairs on 

 the opposite sides of a leaf interlace, like the fingers of two 

 hands clasped together. The sensitiveness resides only in these 

 hair-like processes on the inside, as the leaf may be touched or 

 pressed in any other part witliout sensible effects. The little 

 prisoner is not crushed and suddenly destroyed, as is sometimes 

 supposed, for I have often liberated captive flies and spiders, 

 which sped away as fast as fear or joy could carry them. At 

 other times I have found them enveloped in a fluid of a muci- 

 laginous consistence, which seems to act as a solvent, the insects 

 being more or less consumed in it." 



To Ellis belongs the credit of divining the purpose of the 

 capture of insects by the Diona;a. But Curtis made out the 

 details of the mechanism, by ascertaining the seat of the sensi- 

 tiveness in the leaves ; and he also pointed out that the secretion 

 was not a lure exuded before the capture, but a true digestive 

 fluid poured out, like our own gastric juice after the ingestion 

 of food. 



For another gener.ition the history of this wonderful plant 

 stood still; but in 1868 an American botanist, Mr. Canby, who 

 is happily still engaged in botanical research — while staying in 

 the Diona;a district, studied the habits of the plant pretty care- 

 fully, especially the points which Dr. Curtis had made out. I lis 

 first idea was that "the leaf had the power of dissolving animal 

 matter, which was then allowed to flow along the somewhat 

 trough-like petiole to the root, thus furnishing the plant with 

 highly nitrogenous food." By feeding the leaves with small 

 pieces of beef, he found, however, that these were completely 

 dissolved and absorbed ; the leaf opening again with a dry sur- 

 face, and ready for another meal, though with an appetite some- 

 what jaded. He found that cheese disagreed horribly with the 



leaves, turning them black, and finally killing them. Finally, 

 he details tlie useless struggles of a Curculio to escape, as 

 thoroughly establishing the fact that the fluid already mentioned 

 is actually secreted, and is not the result of the decomposition 

 of the substance which the leaf has seized. The Curculio being 

 of a resolute nature, attempted to eat his way out, — "when 

 discovered he was still alive, and had made a small hole through 

 the side of the leaf, but was evidently becoming very weak. On 

 opening the leaf, the fluid was found in considerable quantity 

 around him, and was without doubt gradually overcoming him. 

 The leaf being again allowed to close upon him, he soon died." 



At the meeting of this Association last year. Dr. Burdon- 

 Sanderson made a communication, which, from its remarkable 

 character, was well worthy of the singular history of this plant ; 

 one by no means closed yet, but in which his observations will 

 head a most interesting chapter. 



It is a generalisation — now almost a household word — that all 

 living things have a common bond of union in a sulistance — 

 always present where life manifests itself — which underlies all 

 their details of structure. This is called //v/c/Zoi-;//. One of its 

 most distinctive properties is its aptitude to contract ; and when 

 in any given organism the particles of protoplasm are so arranged 

 that they act as it were in concert, they produce a cumulative 

 effect which is very manifest in its results. Such a manifestation 

 is found in the contraction of muscle ; and such a manifestation 

 we possibly have also in the contraction of the leaf of Diontea. 



The contraction of muscle is well known to be accompanied 

 by certain electrical phenomena. When we place a fragment of 

 muscle in connection with a delicate g.alvanometer, we find that 

 between the outside surface and a cut surface there is a definite 

 current, due to what is called the electromotive force of the 

 muscle. Now, when the muscle is made to contract, this electro- 

 motive force momentarily disappears. The needle of the gal- 

 vanometer, deflected before, swings back towards the point of 

 rest ; there is what is called a negative variation. All students 

 of the vegetable side of organised nature were astonished to 

 hear from Dr. Sanderson that certain experiments which, at the 

 instigation of Mr. Darwin, he had made, proved to demonstra- 

 tion that when a leaf of Dionxi contracts, the effects produced 

 are precisely similar to those which occur when muscle contracts. 



Not merely, then, are the phenomena of digestion in this 

 wonderful plant like those of animals, but the phenomena of 

 contractility agi'ee with those of animals also. 



Droscra. — Not confined to a single district in the New World, 

 but distributed over the temperate parts of both hemispheres, in 

 sandy and marshy places, are the curious plants called Sundews 

 — the species of the genus Drosera. They are now known to be 

 near congeners of Diontea, a fact which was little more than 

 guessed at when the curious habits which I am about to describe 

 were first discovered. 



Within a year of each other, two persons — one an Englishman, 

 the other a German — observed that the curious hairs which every- 

 one notices on the leaf of Drosera were sensitive. 



This is the account which Mr. Gardom, a Derbyshire botanist, 

 gives of what his friend Mr. Whateley, "an eminent London 

 surgeon," made out in 1780 : — " On inspecting some of the 

 contracted leaves we observed a small insect or fly very closely 

 imprisoned therein, which occasioned some astonishment as to 

 how it happened to get into so confined a situation. Afterwards, 

 on Mr. Whateley 's centrically piessing with a pin other leaves 

 yet in their natural and expanded form, we observed a remark- 

 ably sudden and elastic spring of the leaves, so as to become 

 inverted upwards, and, as it were, encircling the pin, which 

 evidently showed the method by which the fly came into its 

 embarrassing situation." 



This must have been an account given from memory, and 

 represents the movement of the hairs as much more rapid than 

 it really is. 



In July of the preceding year (though the account was not 

 published till two years afterwards). Roth, in Germany, had 

 remarked in Droscra roiundifolia and longi folia, "that many 

 leaves were folded together from the point towards the base, and 

 that all the hairs were bent like a bow, but that there was no 

 apparent change on the leaf-stalk." Upon opening these leaves, 

 he says, "I found in eacli a dead insect ; hence I imagined that 

 this plant, which has some resenililance to the Diomca muscifula, 

 might also have a similar moving power." 



" With a pair of pliers I placed an ant upon the middle of 

 the leaf of D. rotundifolia, but not so as to disturb the plant 

 The ant endeavoured to escape, but was held fast by the clammy 

 juice at the points of the hairs, which was drawn out by its feet 



