Part 3

After contraction has endured for a greater or less time, dependent upon circumstances which we do not well understand, re-expansion of the leaves is effected at an insensibly slow rate, whether or not any object is enclosed, both lobes opening in all ordinary cases at the same time, although each lobe may act to a certain extent independently of the other. The re-expansion is not determined by the sensitive filaments, for these may be cut off close to their bases, or be entirely removed, and re-expansion occur in the usual manner. It is believed that the several layers of cells forming the lower surface of the leaf are always in a state of tension, and that it is owing to this mechanical state, aided probably by fresh fluid being drawn into the cells, that the lobes begin to separate as soon as the contraction of the upper surface diminishes.

Six known genera, Drosophyllum, Roridula, Byblis, Drosera, Dionæa and Aldrovanda comprise the Droseraceæ, all of which capture insects. The first three genera effect this purpose solely by the viscid fluid secreted from their glands, and the last, like Dionæa, which has already been described, through the closing of the blades of the leaf. In these last two genera rapid movement makes up for the loss of viscid secretion. But of all the genera none is more interesting than the typical Sundews.

Growing in poor peaty soil, and sometimes along the borders of ponds where nothing else can grow, certain low herbaceous plants, called Droseras, abound. So small and apparently insignificant are they, that to the ordinary observer they are almost unnoticed. But they have peculiarities of structure and nature that readily distinguish them. Scattered thickly over their leaves are reddish bristles or tentacles, each surmounted by a gland, from which an extremely viscid fluid, sparkling in the sunlight like dew, exudes in transparent drops. Hence the common name of Sundew by which the half-dozen species found in the United States east of the Mississippi River are known. A one-sided raceme, whose flowers open only when the sun shines, crowns a smooth scape, which is devoid of tentacles. _Drosera rotundifolia_, our commonest species, has a wide range, being indigenous to both Europe and America. In the United States it extends from New England to Florida and westward, and is occasionally associated with _Drosera longifolia_, a form with long strap-shaped leaves, but whose distribution is mostly restricted to maritime regions, from Massachusetts to Florida.

All of the species are remarkably similar in habits, capturing insects, and digesting and absorbing the soft parts, a circumstance which explains how these plants can flourish in an extremely poor soil where mosses, which depend almost entirely upon the atmosphere for their nourishment, only can live. Although the leaves of the Droseras at a hasty glance do not appear green, owing to the purple color of the tentacles, yet the superior and inferior surfaces of the blade, the stalks of the central tentacles, and the petioles contain chlorophyll, rendering the best of evidence that the plants obtain and assimilate carbon dioxide from the air. But when the poverty of the soil where these plants grow is considered, it is at once apparent that their supply of nitrogen would be exceedingly small, or quite deficient, unless they had the power of obtaining it from some other source. From captured insects this important element is largely obtained, and thus we are prepared to understand how it is that their roots, which consist of only two or three slightly divided branches, from one-half to one inch in length, and furnished with absorbent hairs, are so poorly developed. From what has been stated it would seem that the roots but serve to imbibe water, but there is no doubt that nutritious matters would also be absorbed were they present in the soil.

With the edges of its leaves curled so as to form a temporary stomach, and with the glands of its closely-inflected tentacles pouring forth their truly acid secretion, which dissolves animal matters that are subsequently absorbed, Drosera may be said to feed like an animal. But, unlike an animal, it drinks by means of its roots, and largely, too, for it would not be able to supply its glands with the necessary viscid fluid. The amount needed is by no means an inconsiderable quantity, as two hundred and seventy drops may sometimes be exposed during a whole day to a glaring sun. Such a profuse exudation implies preparations for hosts of insect visitors. In this Drosera has not miscalculated. Its bright pink blossoms and brilliant, glistening dew lure vast numbers of the smaller kinds, and the larger ones, too, to certain death. But the wholesale destruction of life that goes on is much in excess of what the plant requires for food. While the smaller flies remain adherent to the leaves, affording them the needed aliment, the larger insects, after death, fall around the roots, where they decay and fertilize the soil with nitrogen, which doubtless through the proper channels makes its way into the body of the plant, thus helping to give it tone and vigor. There are times when these plants work better than at others, but whether this is caused by the electrical condition of the atmosphere, or the amount of its contained moisture, is a question which science has not positively determined.

_Drosera longifolia_ folds it leaves entirely around its victim, from the apex down to the petiole after the manner of its vernation, but in _Drosera rotundifolia_, whose marginal tentacles are longer, the tentacles simply curve around the object, the glands touching the substance, like so many mouths receiving nourishment. Experimented upon with raw beef, the tentacles of healthy leaves, from within to without, but in periods of time varying from six to eight or nine hours, clasp firmly the beef, almost concealing it from view. Equally vigorous leaves, however, made no move towards clasping a bit of dry chalk, a chip of flint, or a lump of earth. Bits of raw apple cause a curving of the tentacles, but very few of the glands are seen touching them. It would seem, therefore, that these plants are really carnivorous, preferring animal substances, which they, by the aid of some ferment analogous to pepsin, which is secreted by the glands, are able to absorb. A minute quantity of already soluble animal matter is the exciting cause, and this must be taken in by the glands, or there is no secretion of the fermenting material.

In all ordinary cases the glands alone are susceptible to excitement. When excited, they do not themselves move or change form, but transmit a motor impulse to the bending part of their own and adjoining tentacles, and are thus carried towards the centre of the leaf. Stimulants applied to the glands of the short tentacles on the disc indirectly excite movement of the exterior tentacles, for the stimulus of the glands of the disc acts on the bending part of the latter tentacles, near their bases, and does not first travel up the pedicels to the glands, to be then reflected back to the bending place. Some influence, however, does travel up to the glands, causing them to secrete most copiously, and the secretion to become acid, just such an influence as that which in animals is transmitted along the nerves to glands, modifying their power of secretion, independently of the condition of the blood-vessels. Over organic substances that yield soluble matter the tentacles remain clasped for a much longer time than over those not acted upon by the secretion, or over inorganic objects. That they have the power of rendering organic substances soluble, that is, that they have the power of digestion, is no longer a question of dispute. They certainly have this power, acting on albuminous compounds in exactly the same manner as does the gastric juice of mammals, the digested matter being afterwards absorbed. In animals the digestion of albuminous compounds is effected by means of a ferment, pepsin, together with weak hydrochloric acid, though almost any acid will serve, yet neither pepsin nor an acid by itself has any such power. It has been observed that when the glands of the disc are excited by the contact of any object, especially of one containing nitrogeneous matter, the outer tentacles and often the blade become inflected, the leaf thereby becoming converted into a temporary cup or stomach. The discal glands then secrete more copiously, the secretion becoming acid, and, moreover, some influence being transmitted by them to the glands of the exterior tentacles, causing them to emit a more abundant secretion, which also becomes acid. This secretion is to a certain extent antiseptic, as it checks the appearance of mould and infusoria, and in this particular acts like the gastric juice of the higher animals, which is known to arrest putrefaction by destroying the microzymes.

With animals, according to Schiff, mechanical irritation excites the glands of the stomach to secrete an acid, but not pepsin. There is strong reason to believe, too, that the glands of Drosera, which are continually secreting viscid fluid to replace the losses by evaporation, do not secrete the ferment proper for digestion when mechanically irritated, but only after absorbing certain matters of a nitrogeneous nature. The glands of the stomachs of animals secrete pepsin only after they have absorbed certain soluble substances designated peptogenes, showing a remarkable parallelism between the glands of Drosera and those of the stomach in the secretion of their appropriate acid and ferment.

Not only animal matter, but also the albumen of living seeds, which are injured or killed by the secretion, are acted upon by the glands of Drosera. Matter is likewise absorbed from pollen, and from fresh leaves. The stomachs of vegetable-feeding animals, as is only too well known, possess a similar power of extracting nourishment from such articles. Though properly an insectivorous plant, but as pollen, as well as the seeds and leaves of surrounding plants, cannot fail to be often or occasionally blown upon the glands of Drosera, yet it must be credited with being to a certain extent a vegetable feeder.

That a plant and an animal should secrete the same, or nearly the same, complex digestive fluid, adapted for a similar purpose, is a wonderful fact in physiology, but not more remarkable than the movements of a tentacle consequent upon an impulse received from its own gland, the movement at the bending place of the tentacle being always towards the centre of the leaf, and so it is with all the tentacles when their glands are excited by immersion in a suitable fluid. The short tentacles in the middle part of the disc, however, must be excepted, as these do not bend at all when thus excited. But when the motor impulse comes from one side of the disc, the surrounding tentacles, and even the short ones in the middle of the disc, all bend with precision towards the point of excitement, no matter where it may be located. This is in every way a remarkable phenomenon, for the leaf appears as if endowed with animal sense and intelligence. It is all the more remarkable when the motor impulse strikes the base of a tentacle obliquely to its flattened surface, for then the contraction of the cells must be restricted to one, two or a very few rows at one end, and different sides of the surrounding tentacles must be acted on that all may bend with precision to the point of excitement. The motor impulse, as it spreads from one or more glands across the disc, enters the bases of the surrounding tentacles, and instantly acts on the bending place, but does not first proceed up the tentacles to the glands, causing them to reflect back an impulse to their bases, although some influence is sent up to the glands, whereby their secretion is soon increased and rendered acid. The glands, being thus excited, send back some other influence, dependent neither on increased secretion nor on the inflection of the tentacles, which causes the protoplasm to aggregate in cell beneath cell. This maybe called a reflex action. How it differs from that which proceeds from the nerve-ganglion of an animal, if it differ at all, no one can say. It is probably the only known case of reflex action in the vegetable kingdom.

Concerning the mechanism of the movements and the character of the motor impulse little is known. During the act of inflection fluid surely passes from one part to another of the tentacles. In explanation of the fact it is claimed that the motor impulse is allied in nature to the aggregating process, and that this causes the molecules of the cell-walls to approach each other, as do the molecules of the protoplasm within the cells, thereby causing the cells in all to contract. This is probably the hypothesis that best accords with the observed facts, although some strong objections may be urged against this view. The elasticity of their outer cells, which comes into activity as soon as those on the inner side cease contracting with prepotent force, leads largely to the re-expansion of the tentacles, but there is reason to suspect that fluid is continually and slowly attracted into the outer cells during the act of re-expansion, thus augmenting their tension.

With respect to the structure, movements, constitution and habits of _Dionæa muscipula_ and _Drosera rotundifolia_, as well as kindred species, little has been made out by patient study and investigation in comparison with what remains unexplained and unknown. Many of their movements, especially of Dionæa and Drosera, seem so sensible and intelligent that the reflecting mind of man can hardly hesitate to assign them high positions in organic nature and the possession, even though in a very small degree, of that consciousness with which animal life is endowed. That man is psychically related to all life is the belief of millions in the old world, and the hope of millions in the new. In this thought is the escape from materialism, that threat of the ignorant and unbelieving. Higher conceptions of beauty and greatness are now being entertained by the multitudes, and we begin to feel that the next great step is being taken when we shall become, instead of poor trembling denizens of a perishable world, proud and conscious citizens of an imperishable universe. That we of the upper ranks of God’s creation alone possess an inner life which shall transcend all change is no longer a general belief, but there is a growing hope that all nature shares it, and that love is its expression and its method. All existence is a unit. Life, law and love are divine. Man, looking calmly about him, cannot set himself apart as something essentially different from nature, but must recognize himself as a part, and include love in the universal scheme of development. All other expressions of life must share with him in the divine love and progress. His dogmas, founded on mistaken traditions, have given way to science, and he cannot but believe that love is in and of the soul, and that all life has some sort of development of soul. Because plant-life has no brain, and therefore has no intelligence, no mind, no soul, is preposterous to contemplate. Who can positively affirm that brain alone is the seat of conscious intelligence? None but He alone, the Giver of all life, who sits enthroned and exalted in the everlasting heavens.

SLIME-ANIMALS.

Possibly the simplest of life’s children are the singularly unique and structureless little Finger Slimes, which live not only in the sea but also in puddles and pools, and in the gutters of our streets and of our house-tops. Anywhere that stagnant water abounds these tiny drops of slime will grow up and make it their home. Sometimes few and far between, and sometimes in such immense crowds that the entire pond would seem, if they could be seen with the unaided vision, literally alive with them, they live, and multiply and die under our very feet.

Nothing can be less animal-like than one of these shapeless masses of pure protoplasm, yet under a microscope of strong power it may be seen moving lazily along by pulling out a thick finger of slime and then letting all the rest of its body flow after it. When coming into contact with food it may be said to flow over it, dissolving the soft parts and sending out the hard, indigestible refuse anywhere, no matter where, for its body is devoid of skin, being merely one general mass of homogeneous slime.

But what can these little slime specks tell us about the wonderful powers of life? Nothing at all, it would seem, for in these tiny creatures life has nothing better to work with than a mere drop of living matter, which is all alike throughout, so that if broken into a hundred pieces every piece would be as much a living being as the whole. And yet by means of the wonderful gift of life, with which the all-wise Omnipotence has endowed it, this slime-drop lives, and breathes, and eats, and increases, shrinks away when you touch it, feels for its food, and moves from place to place, changing its shape to form limbs and feeling-threads, which are let into the general organism when they have served the purpose of their existing, only to be succeeded by others as short-lived as themselves when necessity requires their development.

So small are these creatures that the largest specimen will be found to be smaller than the smallest pin’s head. Examine how we will, there will be found no mouth, no stomach, no muscles, no nerves, no parts of any kind. The animal looks merely like a minute drop of gum with fine grains diffused throughout, floating in the water, some times with outstretched arms, and at other times as a simple drop. An analysis of the matter of which it is composed shows it to be much the same as a speck of white-of-egg. Yet it is alive, for it breathes. Kept in a drop of water, it uses up the oxygen it contains, and renders the water foul by the carbonic acid it breathes out. The arms, so necessary in the procurement of food, can be drawn in and thrown out when and where the animal chooses, showing that some option is undoubtedly exercised in the matter. Minute jelly-plants, that live in the water, and even higher animals than itself, constitute its food. The presence of an animal with a shell does not deter it from attack, for it is just as able to deal with it as with the softer, shell-less kinds, sucking their jelly-like contents, and discarding the empty, innutritious shells.

Quite as interesting among the Moners, to which the Finger Slime belongs, is the _Protomyxa aurantiaca_, a shapeless bit of transparent matter, containing merely circulating granules. Locomotion is effected by extending the body into pseudopodia, or false feet, and contracting them. Its movement is slow and gliding. When at rest it appears as a mere lump of jelly, but its whole demeanor changes when in the presence of a living animal suited for food. Fine threads immediately begin to shoot out from all sides, which fuse about the unsuspecting prey, while all the little grains in the slime course to and fro. For five or six hours the little fellow hugs closely round the prey until it has become thoroughly absorbed, at least the nutritious parts, into its body-mass, when it draws itself away, or back into its original place, leaving by its side the skeleton of its late victim. Without eyes or ears or parts of any kind it knows how to find its food; without muscles or limbs it is able to seize it; without a mouth it can suck out its living body, and without a stomach it can digest the food in the midst of its own slime, and cast out the parts for which it has no use.

When Protomyxa has become a burden to itself it divides itself by a simple process of fission, each part being complete in itself, or it assumes a thick covering, becoming encysted, as it is termed. In a little while the enclosed mass divides into spheres, the cell-wall bursts, and the little spheres, which have now taken on a sort of tadpole shape, float out upon the water, where they soon assume the parent-form.

Like all living things, these Moners have a desire for food, which their protoplasm first appropriates, then converts into available material. They thus grow and increase in size, but when they become too large to be comfortable they usually split into two, in obedience to the law of their being, and each half goes its own way as a living animal. This is the earliest form of parentage, the simplest form of reproduction. Thus yielding to this necessity of a separation of one into more than one, these Moners live on forever, or as long as the earth continues to support life, thus becoming immortal in the scientific sense in which the term is used to devote a continuance of the physical life on earth. They only and their nearest relatives, as simple in structure as themselves, achieve this stupendous result, for in such a division of their entire substance they know no loss, no death of any part, violence only being able to sunder them from life. They resolve themselves into their own offspring, and nothing perishes.

PRIMITIVE LASSO-THROWERS.

Every one knows that the long cord or thong, called the lasso, is the peculiar weapon of the South American hunter. Almost from his earliest childhood the young Gaucho learns to amuse himself with it, and as soon as he is able to walk takes great pleasure in catching young birds and other animals around his father’s hut, hurling the long lash with such dexterity that the noose drops over their bodies and brings them to his feet. Did we wish to select from among all the denizens of life the most brilliant, graceful, and sylph-like, whose very life-histories read more like the romance of poetry than sober reality, we would choose those which might be appropriately designated the lasso-throwers.

Now among animals, as is only too well known, any weapons which they could be called upon to use must develop in their own bodies, and therefore it could hardly be suspected that a simple jelly-animal could be provided with a lasso ready grown in its own flesh. Yet it is so, for in that class of animals, which ranks just above the sponges, we discover a weapon of this kind as simple and as deadly, and far more wonderful in its action than any used by man.

In fresh-water ponds, attached by its base to the under surfaces of aquatic plants, may be found a very small animal, just large enough to be seen without the aid of a lens, usually pale green, but sometimes of a brown color. This is our common hydra, technically called _Hydra fusca_. It is nothing more than a tube or sac, with a sucker at one end to hold on with, and a mouth at the other, surrounded with from five to eight hollow tentacles or feelers, which opens into a central cavity or stomach. Firm and muscular are the walls of the sac, so that the little creature, which is not fixed permanently to whatever it is found clinging to, may stretch itself out or draw back as its own volition dictates, or move slowly along by means of its sucker, or float easily or contentedly upon the water. But the most remarkable, as well as the most interesting thing about this odd creature is the power which it possesses of overcoming animals more powerful and active than itself.