230 



HARDWICKE'S SC lENCE-GOSSIP. 



THE CAUNIVOROUS HABITS OF 

 CERTAIN PLANTS. 



DR. HOOKER, President of tlie Royal Society, 

 at the meeting of the British Association at 

 Belfast, whilst acting as President of the Depart- 

 ment of Anatomy and Physiology, gave a most 

 interesting and important address on the above 

 subject, of which the following is a copious abstract. 

 He said that various observers have described with 

 more or less accuracy the habits of such vegetable 

 sportsmen as the Sun-dew, the Venus' Fly-trap, and 

 the Pitcher-plants, but few have inquired into their 

 motives; and the views of those who have most 

 accurately appreciated these have not met with 

 that general acceptance which they deserved. Quite 

 recently the subject has acciuired a new interest, 

 from the researches of Mr. Darwin into the pheno- 

 mena which, accompany the placing albuminous 

 substances on the leaves of Drosera and Pinguicula, 

 and which in the opinion of a very eminent physio- 

 logist, prove, in the case of Dionpea, this plant 

 digests exactly the same substance, and in exactly 

 the same way, that the human stomach does. With 

 these researches Mr. Darwin is still actively en- 

 gaged, and it has been with the view of rendering 

 him such aid as my position and opportunities at 

 Kew afforded me, that I have, under his instruc- 

 tions, examined some other carnivorous plants. In 

 the course of my inquiries I have been led to look 

 into the early history of the whole subject, which I 

 find to be so little known and so interesting that I 

 have thought that a sketch of if^, up to the date of 

 Mr. Darwin's investigation, might prove acceptable 

 to the members of this Association. About 176S, 

 Ellis, a well-known English naturalist, sent to Lin- 

 DfEus a drawing of a plant, to which he gave the 

 poetical name of Dionaia. I will read the account 

 which he gave of it to Linna?us, and which moved 

 the great naturalist to declare that, though he had 

 seen and examined no small number of plants, he 

 had never met with so wonderful a phenomenon : — 

 " The plant . . . shows that Nature may have some 

 views towards its nourishment in forming the upper 

 joint of its leaf like a machine to catch food ; upon 

 the middle of this lies the bait for the unhappy 

 insect that becomes its prey. Many minute red 

 glands that cover its surface, and which perhaps 

 discharge sweet liquor, tempt the poor animal to 

 taste them ; and the instant these tender parts are 

 irritated by its feet, the two lobes rise up, grasp it 

 fast, lock the rows of spines together, and squeeze 

 it to death. And further, lest the strong efforts for 

 life in the creature just taken should serve to dis- 

 engage it, three small erect spines arc fixed near the 

 middle of each lobe, among the glands, that effec- 

 tually put an end to all its struggles. Nor do the 

 lobes ever open again while the dead animal con- 



tinues there. But it is, nevertheless, certain that 

 the plant cannot distinguish an animal from a 

 vegetable or mineral substance ; for if we introduce 

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

 fall as fast as if it was an insect." Linnaeus, how- 

 ever, only saw in these wonderful actions extreme 

 sensitiveness in the leaves, and did not accept 

 Ellis's account of the coup de grace which the 

 insects received from the three stiff hairs in the 

 centre of each lobe of the leaf. For about a century 

 the history of the plant was very little advanced. 

 Sixty years after Linnaeus wrote, Dr. Curtis, of 

 Wilmington, North Carolina, published the follow- 

 ing accurate scientific observations: — "Each half 

 of the leaf is a little concave on the inner side, 

 where are placed three delicate hair-like organs, in 

 such an order that an insect can hardly traverse it 

 without interfering with one of them, when the two 

 sides suddenly collapse and inclose the prey with a 

 force surpassing an insect's efforts to escape. The 

 fringe of hairs of the opposite sides of a leaf inter- 

 lace, 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 without sensible 

 effects." To Ellis belongs the credit of divining 

 the purpose of the capture of insects by the Dionsea ; 

 but Curtis made out the details of the mechanism. 

 For another generation the history of this plant 

 stood still; but in ISGS an American botanist, Mr. 

 Canb.v, while staying in the Dion?ea district, studied 

 the habits of the plant pretty carefully, especially 

 the points which Dr.' Curtis had made out. His 

 first idea was that "the leaf had the power of dis- 

 solving animal matter, which was then allowed to 

 flow along the somewhat trough-like petiole to the 

 root, thus furnishing the plant with highly nitro- 

 genous food." By feeding the leaves with small 

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

 completely dissolved and absorbed ; the leaf open- 

 ing again with a dry surface, and ready for another 

 meal, though with an appetite somewhat jaded. He 

 found that cheese disagreed horribly with the 

 leaves, turning them black, and finally killing them. 

 Finally, he details the useless struggles of 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 sub- 

 stance which the leaf has seized. This 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 inconsiderable quantity 

 around him, and was without doubt gradually over- 

 coming him. The leaf being again allowed to close 

 upon him, he soon died. 



Dr. Hooker then described the character of the 

 communication on this plant made at the last meet- 



