Without reproducing our description of the Dionæa, we may assist our readers’ memory by shortly stating that the leaf of the plant is formed of two lobes joined by a midrib, and that each half of the leaf is furnished with three sensitive hairs. On a fly or other insect settling on the leaf and so irritating these hairs, the two lobes gradually close and imprison the intruder. The most remarkable property of the plant is that it not only kills insects in this way, but that it actually digests them in a manner exceedingly similar to that by which animals are nourished; for after the prey is secured, a liquid secreted in the upper part of the leaf is exuded, and this liquid is analogous with that furnished in the case of animals by the glands of the digestive mucous membrane. The closeness of the analogy will be better understood by referring to an experiment which was made with a view to testing the solvent powers of this secretion. A slice chipped from a dog’s tooth was placed between the lobes of a Dionæa leaf. After some days the lobes were separated, and the piece of tooth was found to be in such a soft fibrous condition that it was torn to shreds by the slight force employed in removing it. This energetic power of the secretion will remind the reader of what we have already said regarding the action of the gastric juice upon the animal tissues after death. Another curious point of similarity between the two fluids is observed in the fact that in both cases the secretion is stimulated by the presence of food.
It seems almost incredible to think how such a peculiarity in a plant should have, until very recent years, remained in obscurity. It is true that more than a century ago an English naturalist described it, and submitted his observations to Linnæus. But since that time the matter had aroused very little interest, until some few years ago when Darwin published his wonderful book on Insectivorous Plants. This want of attention is evidently due to the fact that Linnæus himself merely looked upon the plant as one, like the sensitive plant, having an excitable structure. He regarded the imprisoned insects as merely an accidental occurrence, stating it as his opinion that they were probably released when the leaf re-opened. The matter was thus quietly set at rest by a great authority, and no more was heard of the Dionæa until an able naturalist of North Carolina, where the plant is indigenous, again called attention to it.
Another plant belonging to this group has several peculiarities which are worthy of notice. We allude to the Sarracenia, which is found in the eastern states of North America. This plant grows in bogs and similar moist neighbourhoods. The leaf consists of a trumpet-shaped tube half covered with an arched lid. This tube exhibits a smooth and slippery surface for some distance down its interior; but lower still it is studded with bristles, its lowest depths being filled with a fluid of intoxicating properties. Round the mouth of the pitcher thus formed exude drops of a sweet viscid fluid. The Nepenthes form another branch of the family of Pitcher-plants, including many different species. Indigenous to the Asiatic Archipelago, their appearance is that of a half-shrubby climbing plant, the leaf of which terminates in a long stem, to which is attached a hanging pitcher. These pitchers vary in length from an inch to a foot, or even more; indeed some are large enough to entrap a bird or small quadruped. Their structure is not so complicated as those of the Sarracenia, although in other respects they greatly resemble them; while in both cases the digestive functions are closely allied with those of the Dionæa. But the most seductive of all these traps for unwary insects is certainly the Darlingtonia. Its victim is first of all attracted by the bright colour of its petals, and after it has settled upon the plant, and helped to fertilise it by the movement of its body against the pollen, it slips into a treacherous pitcher, to be first intoxicated, and then totally annihilated. Surely there will be no difficulty in finding an analogy here to certain social institutions belonging to the higher order of animals!
The electrical phenomena common to both plants and animals must next claim our attention. The celebrated Galvani was the first to direct attention to the existence of an electrical current in the muscle of a frog’s leg. Volta disputed this, and insisted that the current produced by Galvani was due to certain metallic connections which he employed, and not to any inherent electricity in the muscle itself. Since Galvani’s time, however, numerous investigators have followed up his researches; and it is now an accepted fact that every exertion of muscular force is accompanied by a current analogous to electricity, the strength of which is in exact proportion to the mechanical power called into play. It is a curious fact that this peculiar force remains in the muscle for a certain time after death, but it is totally lost so soon as rigidity sets in, and no earthly power can recall it. It may therefore be considered as essentially a vital phenomenon. It is moreover greater in mammals than in birds, and is least noticeable in reptiles and fishes. But we must not omit to mention that among the latter are found several which have a powerful electric battery as their chief defensive power. The Mediterranean torpedo—one of the Ray or Skate family of fishes—after which our most modern engines of war are named, is the chief of these.
Although it has long been known that currents of electricity existed in plants, such currents were attributed to chemical reaction between the external moisture and the internal juices of the plants themselves, and also to atmospheric disturbance. They have therefore hitherto borne very little analogy to the muscular electricity of animals. But very recently the subject has received great attention; in fact the electrical disturbance consequent on the excitation of the leaf of our old acquaintance the Dionæa, formed part of the subject of a paper lately read before the Royal Society. The authors of this contribution to our knowledge of a very obscure subject, proved by numerous delicate experiments that the current which accompanied the closure of the leaf in question was in every respect similar to that obtained from the muscles of animals.
[THE BELL-RINGER.]
IN FOUR CHAPTERS.
CHAPTER IV.—THE ANTHEM OF THE BELLS.
It was a solemn gathering when two hours later, the physician entered Bertram’s room in company with Squire Peregrine, Colonel Lindsay, and Gertrude. The change in the Squire was marvellous; his sternness had left him; he followed his daughter and his old friend; he hung upon every word which fell from the lips of the man of science; and during the time when the doctors were alone with their patient and Nathan, he paced his room in a state nearly bordering on mental distraction. Meeting the doctors as they at length emerged from the sick-room, he grasped them by the arm. ‘Will he live? will he live?’ he reiterated wildly. ‘Tell me the truth. My son, my son!’