I have never taken a walk outside without seeing something that was new to me: a plant or animal not yet met before, or some event of plant or animal life. Now it was a cuckoo, quietly calling out, as if no curious one was watching him five paces away, now a rare fern on an old graveyard wall, now reed beetles, just leaving their doll shells or orioles, busy their artfully nest to sew. Fields of orchids of all varieties, a flock of spoonbills on a meadow in the shadow of the capital, nettles dusting in broad daylight, and forest violets with colorless flowers the size of a pinhead—too many to name, in endless variety.
Decades of enjoying nature have already passed and every new spring still brings new joys, new surprises; The number of plants, birds or insects that are marked in the textbooks is decreasing[ 117 ]stand with “very rare” or “found only once” and which my eyes have not delighted with. But how some natural objects can hide! How long it took before I got to see my first gray shrike—that name sounds so dead ordinary—and how well I remember my first encounter with the muskwort and the bearded tits!
I also hope to see a dipper and the nest of a kingfisher and … the water nut.
Water nut (Trapa natans) a. flower, b. pistil, c. fruit. (to Solotnitzky).
Water nut (Trapa natans) a. flower, b. pistil, c. fruit. (to Solotnitzky).
Especially that water nut! I've already roamed about it in some reed-pools and peat-pools, in nooks and crannies that looked as if no man had ever been there, real hiding-places, just fit for a last refuge of a poor persecuted aquatic plant. How lovely could she lie there dreaming of the[ 118 ]time, when she covered ditches and pools everywhere, when her little flowers, supported by the diamond-shaped leaves, floating on their inflated hollow petioles on every still water formed their white carpet.
And that was not so very long ago, not even forty, not thirty years! The misfortune began in 1860, and it is said to have been the fault of a Dutch professor, of a man who should have known better, a man who did not realize what he was doing. And then a scholar! O tempora!
Most likely he knew what he was doing, but then he must have had the feeling of someone standing in front of an open attic window, and who, knowing it will cost him neck, arms, and legs, jumps down, controlled only by the thought: “if only I jumped out!”
But the professor didn't jump out; perhaps later figuratively 'out of his own skin', when he had to hear from well-meaning friends and acquaintances that the consequences of his levity on the municipality of Utrecht soon amounted to several hundred guilders.
And yet he had done nothing but toss a half-withered twig into a ditch—that was all.
But that twig came from a small plant that was cultivated and maintained in the botanical garden—in Leiden people also rejoiced in having a cup full—because it was an aquatic plant. And a curious plant, too, from the land of the yellow fever and the Colorado potato beetle, and widely known by the less beautiful name of Waterweed. Now I imagine that his scholar had read of the prodigious vigor of this little plant and how in the last twenty years—that is, after 1840—in the north of England it had grown so much that it affected navigation on the canals. [ 119 ]very seriously hindered .. and there he now stood in front of the attic window. Would it grow that fast here too? What if I threw this twig into the water? The canals have just been cleaned; so it can rest for a while. But those clogged canals at Berwick!
(Elodea canadensis.) Waterweed.
(Elodea canadensis.) Waterweed.
The twig was in the water. If only the man had gone after it—to get it out again. For the thing has started to grow, to grow, and our inland shipping is suffering from it, just as much as the English 50 years ago—now also, of course—our ditches are full of it. Not only ours, but those of all of northern Germany, last year as far as Poland!
Immediately the sentence of the water nut was signed. Like most aquatic plants, it seeks shelter in winter at the bottom of ditches and pools, in the mud—just like the frogs sometimes do. And the sweet spring, which calls the cheerful quacks to new life, also awakens the dormant buds of plants. There are those who wake up early, but the late sleepers are not lacking either; our water nut is one of those, and it has cost him dear. For if the sluggish European seeks awakening light and air, the shrewd Canadian with truly American agility and vigor has already preceded him and has occupied all the places. The[ 120 ]young waternut sprouts cannot come to the surface, they languish for lack of air and light and do not even get to the point where they can form blossoms or new buds. Thus their race has been displaced and extinct, as in the far West the red man and the bison disappear once the pale face has shown itself.
Now the question is: did the Dutch flora win in the exchange? We have already seen that Elodea can become a nuisance for navigation, and that has never occurred to me about the water nut.
On the other hand, the waterweed is a very nice addition to the aquarium, where it can be easily grown. Just be like the professor; take a piece of leafy stem and throw it in the water. In a few days white thread-like roots develop, reaching the sandy bottom of your pelvis; very soon the stem fragment branches, and the emerald-green stems with the somewhat darker leaves meander gracefully through the water and seem to illuminate it with a green glow. The water is actually clarified by the plant. You can test it by deliberately making the water of your aquarium cloudy before planting waterweed, that is, throwing dirty water in it, for your bottom sand will be so clean that stirring it will not cause "turbidity". caused. Then you have put dirty water in your aquarium—of course with a suicidal feeling—and then Waterweed—it can hardly get any worse, you will think—but within twenty-four hours the water is as clear as crystal and the plant shines like a gemstone. Where has the dirt gone? That remains a mystery for now.
It goes without saying that the water plague purifies this[ 121 ]possesses power in the wild equally or to a greater extent; and when you go out on fresh, sunny April days to watch the awakening life of nature and you can see the smallest animals at the bottom in the crystal-clear water, you owe that a great deal to the foreign intruder. to thank.
In July and August the Waterweed blooms with small lilac or purplish-red flowers on peduncles so long that the flowers float just on the surface of the water. If you do not deliberately seek them, you will not easily find them; but it's worth it, and you can look forward to larvae and eggs of aquatic insects at the same time.
The flower shell consists of six dots, within which there is a three-part stigma. On closer examination it appears that this stigma is the end of a long threadlike style, which arises from the ovary at the very bottom of the pedicel. At once we see that the flowers are sessile, and that what we thought to be a stem should really be called a corolla or calyx or something like that.
Stamens are not present in this flower.
Well, you say, then the flower is female, let us see if there are no males on the same plant.
No, no male flowers to be found; so the plant is dioecious, we may still find a male specimen in this ditch, or a little further.
Don't search; There is no male Waterweed in the Netherlands and not in Europe either.
And that is very unfortunate. For the Waterweed has a manner of blooming which is among the most remarkable, and whose wondrousness is surpassed by but one plant; it has therefore in the world of plant experts, plant lovers and aquarium friends [ 122 ](to speak with the Germans) acquired a great reputation.
The male flowers of our Waterweed contain nine stamens—a rather unusual number, too. By the time those stamens are "ripe"—that is, when they begin to burst open and release their pollen—the entire male flower detaches from the plant on which it has developed to float freely in the water. The anthers, covered with sticky pollen, then protrude beyond the inflorescence—they look overboard. On the slender boats float on the reflecting plane—no storms blow in July and August. Where are they drifting? Some of the shorelines are lost, others remain off the shore and end up with the female flowers, which lie flush with the water, and whose protruding stigmas come into contact with the anthers. Some pollen grains stick to the stigmata,
Essentially this manner of flowering is the same as with the Vallisneria spiralis, the famous plant of which I have just spoken. This grows wild in southern Europe, but every aquarium enthusiast owns a few plants and will gladly give you a cutting. They take root in the soil and grow wholly submerged, long band-like green leaves standing erect—curved slightly apart. If they have good light, they will also flower in the aquarium and that is worth it.
Vallisneria spiralis.
Vallisneria spiralis.
Some plants develop green buds, under water, on straight stems of 1 to 2 cm. long, others get similar buttons, but they are on a long stem, which is twisted together like a corkscrew. After a while the corkscrew stretches until the knob has reached the surface of the water. Over there[ 125 ]it opens and now it appears to consist of 3 light green leaves, within which an ovary with three styles, which protrude over the water outside the flower. (Drawing p. 121 right).
Meanwhile, something has happened to the buds that sat on the straight stems. Those stalks are very brittle: they break at the slightest touch, when it's their time. The buds, which are lighter than the water, then rise and float on the surface. Now you would think they were over—a torn part of a plant must die. But our Vallisneria buds live on for a while. They open as if they were still part of the plant, and the stamens inside the three petals ripen and bend outwards.
Those leaves each resemble a boat, three boats together form a flower, which is carried by wind and current. If such a stamen boat now floats against a pistil flower, the anthers touch exactly to the stigmas, to which the sticky pollen then remains attached. But now comes the best. You would now think: the stigmas are provided with pollen, so now the seeds can ripen. That's true, but they don't have to stay above water to ripen—it's much safer down there—and what happens now? The stem curls back into its previous corkscrew shape and pulls the ripening fruit with it into the green depths.
It is not yet known exactly whether the Waterweed does exactly that. It has been observed that stamen boats sail to the pistil flowers, but it is not yet possible to say with certainty whether the fruit also ripens under water. That is because the waterweed rarely blooms in its own homeland; the male flowers are rare and fruits and seeds unknown.[ 126 ]
But because of the wonderful vitality and the incredible capacity for development of the torn stem parts, the survival of the plant is assured for long years, but one day it will come to an end; According to some botanists, waterweed is already on the decline in England. When an unusual movement in the water snaps and destroys its brittle stems in a way that would kill any other plant, it has only the effect of making every fragment start a new life elsewhere.
In the summer, see a flock of ducks busy in the shallow pool, completely overgrown with aquatic plants! That is a tugging and pulling and sniffing and beaking without delay; duckweed and waterweed are torn and swallowed up for the little beasts that dwell in and between them, while from time to time one or more dive to the bottom to get heavier fare. They're all drakes—the female ducks are all brooding. Let's sneak a little closer to see what species are represented, because there are ducks and ducks.
Carefully! The hunt is not yet open, and the hail is not yet in their minds, but there is no more suspicious fowl than ducks, and perhaps the poachers have already been busy. There are those guys who always have to shoot!
Kwêk—one of them has already seen us and is running away. Those closest to him also sensed trouble and followed him. Their passing causes a stir among the rest, and so in a short time the whole swarm has gradually disappeared, scattered in all directions.
Flowering of the Valisneria spiralis.
Flowering of the Valisneria spiralis.
In the middle a pistil flower; left and right floating stamen flowers, (Chalk drawing, partly after Kerner).
Where to? To another pool, or to the ditches in the meadows, where the purple orchids and the red cuckoo flower mark the time of year. Ironing there [ 129 ]down, and, house-trained beasts as they are, their first work is to cleanse themselves of whatever has become lodged in their feathers in their hasty flight from the pool. One by one, the flight feathers and tail feathers are sanded off, a mad dip decides to make the toilet, and the result: duckweed plants and ... pieces of waterweed float in the ditch.
Within a few months the ditch is full - much to the chagrin of the farmer - who already dreads draft mowing and the polder chimney and already outweighs the possible advantage of fertilizer and raising the edge against the wages to be paid for ditch cleaning.
If the annual ditch cleaning did not take place, there would very soon be no more ditches. The waterweed and its confreres would soon occupy all available space—much to their own detriment, of course; for once they had turned the water into peat mud, they could grow no more themselves, and would be inferior to the mud plants. So that, in the end, the annual great slaughter of aquatic plants once again turns to their own advantage.
Who are the confreres of the waterweed? Which Dutchmen can still lead a quiet life besides the dangerous American? Those plants, of course, which most resemble him, and nearly resemble him in manner of life,—first of all, the hornwort and the featherweed. These are both plants, which, like the waterweed, with their long stems, wreathed in leaves, permeate the whole body of water. Their leaves do not spread like those of the clumps and duckweed, on the surface of the water—but even in the deeper layers of water they still find what they need for their existence. This property makes them particularly suitable for aquarium plants, not only because their emerald green garlands[ 130 ]and festoons brighten up the colorless body of water, and give a double glow to the red fins of perch or reed burrow—but also because of the beneficial influence they exert on the water itself, and which would be almost entirely absent if they lived only on the surface.
Hornwort (Ceratophyilum submersum). Separately: a leaf axil with flowers.
Hornwort (Ceratophyilum submersum). Separately: a leaf axil with flowers.
You are already guessing what that beneficial influence is. Like waterweed, hornwort and featherweed possess the ability,[ 131 ]to purify the water of the sludge particles that float in it—though in a different way. In the case of waterweed, it remains a mystery where the mud particles have gone, since neither the plant nor the soil show any trace of them—at the hornwort they settle on the outer skin of the spiky, tough, flexible leaves, until the whole plant covered with a layer of mud.
It is thus easy to clean a cloudy aquarium by always placing clean hornwort in it. If it finally doesn't work at all, then it is a fait accompli, the water is pure. Impurity caused by vegetal or animal corpses, however, cannot be remedied in this way—for that purpose, as has already been said, use the siphon diligently!
That cleaning service is now very nice and good—you will say—but I can keep my aquarium clean too, and I'll be careful not to put clay in it. For that alone Elodea and Ceratophyllum and Myriophyllum need not be so glorified! You are, of course, quite right—but there is more.
Take again one of those candy bottles you use on your hunting trips for small waterfowl, but choose a very light one; save the green ones in case you have animals to be segregated, such as the yellow-rimmed water beetles and their larvae or similar predators. Now go to your ditch (every nature lover naturally has a ditch, a swamp, a bush, etc. near his residence where he can always find the most common plants and animals for immediate observation) and fill your bottle with fresh, healthy branches of the three plants I've just come to talk about. Do some of those long green threads that float in all ditches sometimes slip into the bottle, that's so bad[ 132 ]not—not even if a few pieces of duckweed come in—they'll all join in anyway. Fill the bottle quite full—of course not so that the plants are pressed together, but they may still fill the bottle from bottom to top. Of course there are also small animals among them, but I would prefer that their number was as small as possible; only then can we ascribe what will happen in our bottle to the activity of the plants.
Now home; watch a bucket with water and a deep plate get there and chase all the curious out of the kitchen. Now take the bottle with the plants and submerge it in the bucket of water, then place the hollow of the deep plate on the opening of the bottle, and now turn bottle and plate over—always making sure that both remain submerged. Then take hold of the plate now at the bottom—as one usually takes a plate with two hands—and lift the plate and bottle out of the bucket. The plate is then full of water—the bottle, which is upside down on it, too—you have long known by which laws of physics, and you immediately remember everything about the pressure of the air and communicating vessels and barometers and the like.
If the rim of the bottle is very clean and the bottom of the plate is just flat, then there are no communicating vessels; the water in the bottle is then completely closed off from that in the plate, but—I just don't want that. So if you are afraid that the water from the bottle may not get freely into the plate, cut four slices from a cork and slide it carefully under the bottle rim, taking care, of course, that the rim does not rise above, otherwise it will run. empty the bottle and then you can start from the beginning. Now no Dutch housemother will want to tolerate your spillage in her house, so put your device in a bright spot in the garden or in the garden.[ 133 ]windowsill. You may remove so much water from the plate that it does not overflow; but beware that the rim of the bottle does not rise above water, or, etc.
Now there must be French themes to be made, or sums, or you still have to draw a map of Central America; so leave the device to its fate and come and have a look in a few hours.
Don't get angry all at once, and don't say that Johan has touched it again and that you can see it, because the deep plate overflows and that air has entered the bottle. Rest assured, Johan was not even there and the maid did not tinker with it either. Convince yourself. Squirt some water out of the deep plate—then sit next to it—watching over your treasures. Within a short time the air space at the top of the bottle has become larger, the plate seems fuller and soon it overflows. The air, or whatever it is, develops in the bottle itself! However, this development gradually slows down and finally ceases completely, or becomes imperceptible. If you leave the whole thing standing for a few more days, then the plants will die.
Air or whatever it may be! Let us examine what we got in the bottle. It is a colorless gas. What colorless gases do you know? Air, light gas, carbon dioxide, hydrogen, oxygen, there are already five—or four and a mixed bag, as you know. Now call for Johan and your sisters, if you have them, and the maid (they can scream if necessary, that is more satisfying). We will immediately take the fire test, accidents will not happen, I guarantee that. One has to keep the match ready, another to close the bottle under water (with a wet piece of cardboard, or rather with a well-fitting large cork) and stand up.
Now if we keep the burning match in our “gas” , [ 134 ]different things can happen. The match continues to burn quietly, then it is ordinary air; the gas explodes with a red or yellow flame, then it's light gas. In carbon dioxide, the match goes out, and hydrogen explodes with a blue flame. None of that happens, but the match itself suddenly starts to burn blindingly brightly, giving us the certainty that oxygen has arisen in our bottle.
from what? and why? We cannot say that at once, for that we have to repeat the test—(we always spoke of 'the great test' at home)—a few more times, under different circumstances.
We set up everything exactly like this again, only instead of putting plants, animals, eg thorns in the bottle. The spines die in a few days, but you do not observe any gas development. Now fill the bottle again with plants, but cover it on the outside with thick black paper. Even now we get no oxygen, or only a little bit, from which it follows that the plants we have had in our bottle produce oxygen under the influence of the sunlight. So they are like gas factories.
If you want to do it more beautiful and simpler, buy a cooking bottle of thin glass of half a liter capacity. Fill it completely with water and water plants and close it with a cork with a glass tube through it, which comes almost to the bottom of the bottle. Just put the bottle in the light and after a short time the neck will be full of oxygen.
Oxygen is constantly rising from your aquarium itself in tiny bubbles, usually so small that they go unnoticed. If you look carefully through an upright wall in your aquarium, you can see very fine perpendicular threads hanging in the water, thin pearl strings; they consist of very small oxygen bubbles, which [ 135 ]rise, but you can hardly see that, because the bubbles are so equal in size and always keep the same distance from each other, that there is no change, no movement, in the thread. Yet you can convince yourself of it. Above a spot where some of those pearls hang close together, place an inverted glass funnel or test tube filled with water, and after a while the water will have gone out and been replaced by oxygen. It will take you some effort to keep the funnel or tube still for a while—a few hours—over the rising bubbles, but I trust in your patience and ingenuity, and in the judicious use of bits of cork and ends of iron wire, have, of course, amassed large stocks. After all, every boy has an “arsenal”,
It is a great satisfaction for us Netherlanders to know that this extremely important experiment, and the great discovery about the life of plants that resulted from it, were first made more than a century ago by a compatriot, the famous Jan Ingenhouss van Breda.
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