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The duckweed needs its roots

 If you keep Utricularias in a bowl of clean water, they will wither, no matter how well you provide plenty of light. They cannot thrive in clear ditches, where there are no small aquatic creatures. They are literally starving, they cannot absorb enough nutrients from the water: they have to be fed! They are so accustomed to fatty broth that the thin water porridge with which other plants are content makes them sick.


You now also understand that the Bladderwort does not need roots, like the duckweed, for example. The leaves more or less serve the purpose of it: nevertheless they absorb the dissolved nutrients. The hornwort seldom has roots either, it is so completely surrounded by the nourishing water that it is completely permeated by it of its own accord. That "by itself" is of course in a manner of speaking—I mean about the same as when I say that water, in which a pig 's bladder is suspended full of milk, turns itself into water and milk—the milk in the bladder too—you understand again: Physics, Chapter so much, on Osmosis.


The duckweed needs its roots; the underside of the plant alone would not be able to absorb enough. Waterweed could do without roots as far as food is concerned, but he needs them for something else. Most aquatic plants have roots that either hang freely in the water, as in duckweed, or cling to the ground as in waterweed, yarrow, water lilies, water gentians, pondweeds, etc.[ 157 ]


Vesicles of the bladderwort with prey.  At 5 the inner wall with suction cells is very much enlarged.

Vesicles of the bladderwort with prey. At 5 the inner wall with suction cells is very much enlarged.


[ 159 ]


The roots come in handy when the ditch empties or dries out. I have already told you that duckweed will not then share the fate of the fish, but will resign itself to continue to live on the mud.


Yes, the fish die when the ditch dries up, save the eels; they creep at night through the grass, wet with dew, to another water palace. Larvae pupate on such an occasion, if they are not too young; I need not tell you that the frogs and salamanders and beetles manage to get by. Very small aquatic creatures wrap themselves in a double skin during drought, so they sleep over the drying time and are revived by a puddle of rain.


Now most aquatic plants, which take root in the soil, can withstand adversity well. Utricularia and hornwort die inexorably, but yarrow and waterweed and the pondweeds are tough. If the period of drought lasts a little long, their branches wither and die, but the plants themselves are not yet dead.


When the ditch fills up again, new branches sprout from the bottom. These plants are so careful not to expose themselves entirely—their actual bodies are hidden in the damp mud, and are left there waiting for better times. If you dig a ditch bottom, you will easily find those stems or rhizomes. They sometimes retain their vitality for a very long time; years after the drying out for some reason, when the ditch fills up again, immediately leafy stems and flowers develop again. If the drought lasts for a long time, they must finally die, or change their way of life and become terrestrial plants.


However, the latter is only possible for a few; welfare[ 160 ]there are plenty of plants for which it seems rather indifferent whether they are in the water or not—reeds, blistering buttercup, watercress, fieldcress—but these are in fact all real land plants that can withstand a little moisture. Whether they are in the water or not does not change their appearance.


water clover.  After a watercolor by Ben Reith in Maarssen.

water clover. After a watercolor by Ben Reith in Maarssen.


But now go and search with me again in July or August from aquatic plants—perhaps we will also find the much-wanted duckweed flowers—then I'll show you another curious little plant. We don't have to search many wide ditches—especially if the water isn't too brackish and dirty, or we've found it. A number of pointed-oval leaves (8 to 9 cm. by 3) float flat on the water, similar to those of the floating pondweed (the tea leaves), but narrower and more pointed, yellow-green in colour. A dM rises in the midst of those leaves. high, some richly flowered, rose-red spikes, the sweetest little flowers—something to look at as well.


Let's try to grow such a plant. It grows far from the shore, so the hook has to be involved and it is not very easy either, the cherry-red flower spike keeps slipping out from under the fork: the plant is firmly rooted in the soil. Now you can grab the tip, hold and pull gently—with little tugs, or the stem will break off. Handsome—it's already broken—broken at the root. What do we have now?


One and a half meters of limp stem, from which long limp stems sprout from distance to distance, bearing the leaves already mentioned at their ends. Actually don't carry, the stems are so limp that they can't even carry themselves; they bind the leaves to the stem, shall we say. The end of the stem, the red flower spike, is firmer: you can keep it upright—but otherwise[ 161 ]the whole plant is a tightrope of history—slack and smooth; everything lies in a lame heap on the grass.


Why should an aquatic plant be sturdy? Yes, a tree must be strong or it will blow over, and the slender stalks of wheat must be strong enough to hold up the ears—but an aquatic plant? It finds sufficient support in the water, as long as its buoyancy is not lost; and this has been taken care of, because stems and stems and leaves are provided with air spaces, swim bladders as it were. Thus an aquatic plant stands upright in the same way as a stick, at the end of which you have tied a stone with a string, remains upright in the water. Duckweed floats on the white hollow tissue that can be seen on the opposite side of the leaves; the triangular duckweed misses that and therefore does not float, but floats like the hornwort, all according to the same law of Archimedes.


Now you also understand why the bloomer of our moor root (Polygonum Amphibium)—that's the name of the plant we caught—must be so firm, it has no support from the water waiting. Let's take another look at the plant. You notice that the lower petioles are longer than the upper ones—correctly, you say, that is, because all the leaves must float on the water, and therefore must be level.


All right, but now imagine this. Now when the petioles are all just that long, and their ends, where the leaf blade is attached, reaches the surface of the water, then the twelve to twenty leaves of our plant come close together, three or four clumped together. to lie on the top of the stem—not an advantageous arrangement really, when you consider that each leaf must absorb nourishing air with its surface. There must be a flaw in our reasoning.


Just look in the ditch; that raises even more[ 162 ]our rose- red spikes, and there the leaves are not so close together, there are even quite large spaces of water between them. How is this taken care of. Dead simple. The stems, the beginning of which is 20 cm. under water are not 20 but 30 cm. long. They lack the strength, for their leaf blade which is 10 cm. above the water, the leaf blade must lie on the water, the stem, which cannot hang up in a bend due to its buoyancy, comes obliquely stretched into the water and the leaf blade is 15 or 20 cm. away from the flower spike—thus the lower leaves are furthest from the stem, and each leaf has plenty of space and air.


Leaves of the Cranberry (Polygonum amphibium) left water form, right land form.

Leaves of the Cranberry (Polygonum amphibium) left water form, right land form.


Put our catch in the planter box now—botanising jar they say in the shops—we'll have to look at it again later, I hope. Now leave those duckweed plants alone, you won't find the flowers and I have something else in store.


This ditch used to be higher, but for a few years the polder level was lowered; a little pond at the end of the ditch has run dry and has now become a low, bad meadow—still wet and full of rubbish.


Also a multitude of red flower spikes. Compare them with what we in[ 163 ]have the bus and you will see that the flowers match exactly!


But the plants themselves differ as the crow flies—here in the land plant there is no trace of that smooth, limp and elongated. The stem is moderately long, thick and sturdy, the petioles short and strong, the leaves themselves shaggy and brown and sticky. The whole plant is sticky. And yet we are dealing here with the same plant. When we germinate its seeds on the bottom of the water, the water form develops, while when germinated on dry land the landform appears. If a ditch in which the water form grows runs dry, the stem and leaves sink impotently to the bottom and die there, but the rhizome continues to live in the bottom and develops this year—if the season is too far advanced, in the following year—a stout shaggy stem with short-stalked sticky hairy leaves.


A plant of this kind has even been found in our country, which had developed two stems from its rhizome; one in the water, the other on land. Leaves and stems of the two halves did not resemble each other at all, but had taken on the shape that suited them best in their circumstances.


What does that stickiness mean? The flower must teach us that. Just now, when we compared the flowers, you had occasion to see that they are small, but very gracefully formed. If you look at one of the more than a hundred flowers of the flower spike separately, you will notice that a calyx is missing and that the corolla is a fine pink-red five-pointed bell, within which 5 stamens and 2 styles. At the bottom, between the stamens, you see five yellow spots on the crown. Maybe they shine a little. That's because honey is isolated there, quite a lot[ 164 ]also. That honey —the flower is very proud of it and at the same time very frugal with it. The whole world must know, that is, the whole insect world—another do not know the flowers among us—and the announcement is made in two ways.


Firstly because of the colour: the accumulation of hundreds of flowers on a spike makes them stand out from afar, and then because of a fine penetrating scent, which not only fills the olfactory nerves of us humans, but also those of pleasantly caresses the six -legged honey candy. You know that the latter have the olfactory nerves in their antennae—two mobile noses!


You can be sure that a fly, or a bee, or a little bumblebee, will sense that smell, then it will look around and immediately aim for the beautiful red rod. There we immediately see the 5 yellow spots in a crown, they have known for a long time what that means, they hastily grab the flower, stick head and tongue in and feast. Startled as they are, they have robbed the flower of its goodies in seconds; in this way they finish the whole rod and then float on.


Now, however, our peat roots or water many nodes have a special arrangement. Look for a few different flower sprigs together and then investigate the length of the stamens and styles, and you will immediately notice that the styles and stamens in no flower are of equal length. But also—that in some inflorescences the stigmas are so long that they protrude beyond the corolla, while the short stamens do not reach the margin. In other flowering spikes it is the other way around: there the styles are hidden in the crown and the stamens protrude far out. Now what is this good for?


Of course for the cross-pollination. Check it out. When an insect, a small bumblebee for example on a flower[ 165 ]with long stamens, comes to look for his mouthful of honey, then he must touch the five anthers with his shaggy underside. The sticky pollen gets stuck in his hair. He does touch the stamps of the styles with his head. Now he continues. If he now comes to a 'short-styled' flower, he will get even more pollen on his belly. However, when he visits a "long-styled" flower, its stigmas just touch the spot on the underside of its body, where all the pollen from the short-style flowers is. These stigmas are sticky—the pollen partially adheres to them when the bumblebee leaves, and the eggs in the ovary can develop into germinating seeds.


Peatroot (Polygonum amphibium).  Long-styled flower.

Peatroot (Polygonum amphibium). Long-styled flower.


Peatroot (Polygonum amphibium.) Short-styled flower.

Peatroot (Polygonum amphibium.) Short-styled flower.


Our bumblebee, which flies away, has also received a souvenir from this flower from the short stamens, which were hidden in the crown and whose pollen is now stuck to the hairs of its head and snout. You can count on your fingers, so to speak, that short-styled flowers are fertilized with this again.


The water polynomial thus provides cross-pollination by having two forms of flowers—the botanists, therefore, say in a learned Greek word,[ 166 ]that he is dimorph (di, 2, morph = form). They also call him hetero-style (ie unequal in styles).


The flying insects take care of the transmission of the pollen, which are rewarded with honey for this service —the wingless may refrain from the sweets.


As long as our plant grows in water, only winged guests can visit it, but on land—it's different there. There the long-legged, smooth-bodied ants, so greedy for sweets, would have consumed the whole supply of honey in no time , without doing the least bit for the benefit of the plant itself. Such an ant eats it all up, ambles down, perhaps without a single grain of pollen on its smooth body, or if it has accidentally picked up one, then it loses it along the way, because it bangs against a stalk of grass, from a clod rolls down, or because some other ant accident strikes it. That's why our plant doesn't wait for a visit from ants, but politely—or impolitely—refers them entry.


When an ant gets it in his thick head to taste polygonum honey , and he climbs up a stalk, he doesn't come every time, and again and again his feet stay on the sticky hairs with which the whole plant is covered, stuck and if he doesn't turn around soon—he could get stuck for good and starve to death.


Wouldn't you have to admit that such a polygonal knows how to arrange things neatly?


There are not many red flowers in the water, most are yellow or white—I actually only know one, the water violet (Hottonia palustris), but it is much more beautiful than our peat root—can also be found from May Bee[ 167 ]thousands, everywhere, but not in too brackish water. Around Amsterdam is a magic circle, into which Hottonia cannot enter; de linie Geinbrug, Abcoude, Uithoorn Aalsmeer, Haarlemmermeer (about the same as what in our military sciences is now called the 'thesis Amsterdam'.).


But first I'll tell you what the flower looks like. A slender, straight stem of 2–6 dM rises above the water surface. height, bearing five to ten whorls at its apex, each consisting of 3 to 6 large pale red flowers, clearly reminiscent of primroses—pentagon with a yellow pentagonal center. I always think of chandeliers or candlesticks when I see those flowers, or when I imagine them. They are so erect, and the flowers are directed laterally, so that their largest area of ​​color is conspicuous.


Short-styled flower of Hottonia palustris.

Short-styled flower of Hottonia palustris.


I will never forget how on a wet May day in 1994 we found the ditches and lakes between Ankeveen and Uitermeer full of Hottonia. There was a ditch, straight, 2 K. M. long, there they stood in an endless row; just in front of us the sky whorls shone separately, but beyond that everything melted into a rose-red, ruddy flower. Right and left alike.


If you want to have a nice aquarium with flowers in May, collect water violets that are still in bud in the first days of the month. Carefully pull them out of the ditch, the plant is very brittle, you don't need roots, if you but take care, intact, to take with you the finely divided finned leaves, which lie spread out under the water, and from whose midst the flowering stem rises.[ 168 ]


At the same time, in swampy places you can look forward to an even more beautiful flower, the most beautiful flower from our puddles and swamps, the water trefoil. It is a bit too big for an aquarium, but can be grown very well in a tub with clay, which you keep as wet as possible. Besides the beautiful buds, the plant attracts attention because of the beautiful white frizzy hairs on the inside of the crown. Nobody knows what they are for.


Water violets and water trileaf are both dimorphic, as is our peat root. So you have to make sure to find both shapes, those with long stiles and those with short stiles. It's not difficult because they usually grow together.


Most ditch flowers are white. You immediately think of the white lumps of which you have already heard so much and which so often make the poets dream on the water like 'water lilies'.


Long-styled flower of Hottonia palustris.

Long-styled flower of Hottonia palustris.


The water lilies are the largest flowers in the Netherlands, the white ones at least, they grow up to 12 cm. in cross section. This is a very sober start to speak of these delightful flowers, but they are simply not daisies, and their size is what makes them so widely admired. There are plenty of flowers, finer in composition, more tender in colour, more admirable in arrangement, that most people do not know—who used to adore the water trefoil or the marsh an-thorn?


But the clumps are so brilliant, so large, so profuse, and they bloom for weeks at a time at the most glorious time of the year, like the song of the nightingale, or—whichever suits them better—that of the marsh-reed warbler.[ 169 ]Even if you have little literacy, you know how from the banks of the Nile to faraway Japan the lotos is revered—the lotos, which is nothing but a lilac plum, whose flowers rise a little higher above the water and more odorous than ours—they are the symbol of tranquility and purity.


Another relative is the Victoria regia, the queen of the Amazon River, whose leaves can support the weight of a man.


With us only the swift moorhens walk on the round leaves, or a green frog comes to sunbathe, and preys on fat flies and slender damselflies. There are certainly Hydras on the undersides of the leaves, and the thick hollow petioles, erect by their buoyancy, are full of the eggs of snails and fish.


They owe this motive power to the countless air chambers they contain. The interior of an aquatic plant stem is always so spongy. That's nice. A land plant makes every effort to be full of water to the top; It is almost impossible to understand how a tree thirty or forty meters high has to build it, but he succeeds anyway. Aquatic plants, on the other hand, are always out to have air supply in all their parts, they have enough water, but air is equally indispensable. You should never forget that.


A plant needs fresh air as much as an animal, and for the same reason. In the "great trial" we saw that the plants consume carbon dioxide and then give off oxygen. You might now think that a plant placed in carbon dioxide alone would be quite pleased with it. Wrong! He would choke on it and die, just as much as a mouse or a frog.


Plants need that all their parts provide[ 170 ]can be obtained from fresh oxygen. The thick rhizomes of the water lily, which are hidden in the mud at the very bottom of the ditch, must breathe, must have fresh air. And it is supplied to them by the air ducts in the thick petioles, which are thus of the utmost importance for the life of the plant.



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