How seeds and fruits are distributed diagram. Distribution of fruits and seeds – Knowledge Hypermarket

After seed formation, either the entire fruit or the seed (or seed) it contains is separated from the parent plant. The methods of dispersal of seeds and fruits in flowering plants are very diverse. Of course, wind and water are widely used here as mediators in settlement, but they are also supplemented by the mediation of animals, as well as the use mechanical forces, arising in the plant itself, and, in addition, numerous adaptations of the fruit that allow the most effective use of the listed intermediaries.

There are three main external factors that spread seeds,

1) spread by wind (anemochoria);

2) distribution by animals (zoochory);

3) distribution by water (hydrochoria).

Distribution by animals

Animal seed dispersal is generally more reliable, as animals tend to visit fertile areas suitable for seed germination. The fruits, equipped with spines or hooks, cling to the skin or fur of passing animals and can be carried some distance before being picked off or falling off. Trailers develop from different parts fetus or surrounding structures .

Rice. 1. Fruits distributed by animals

Examples are the fruits of bedstraw, gravilat, burdock, carrots, buttercup, string, and agrimony.

Examples juicy fruits Serve the fruits of plums, blackberries, strawberries, tomatoes, and apple trees. The fleshy parts of these fruits serve as food for animals and birds. When mature they usually acquire bright color and aroma that attract animals. The animal eats it and the seeds pass through the intestines and are excreted, often landing on fertile soil. Contained in excrement nutrients can increase the fertility of the soil around the seed.

Wind propagation

Many wind-dispersed plants have special devices. These include volatiles, which are supplied, for example, with the seeds of willow, fireweed, cotton, dandelion fruits, and lionfish, such as pine (gymnosperms), ulcer, ash, maple, hornbeam.

Rice. 2. Fruits and seeds distributed by the wind

In a number of plants, for example, poppy, nigella, foxglove, lychnis, the fruit is a capsule sitting on a stalk, which is swayed by the wind, so that numerous small seeds spill out through the pores in the upper part of the fruit.

The seeds of some plants, for example, orchids, are so small and light that they are carried by the wind, without any special appendages or dehiscent fruits. Their opening occurs by cracking along the seam between the carpels, as, for example, in beans. In this case, the seeds are either thrown out of the fruits with a more or less strong push, or simply fall out of them. Some of these seeds have adaptations for dispersal by wind (for example, fireweed). The capsules can also be dehiscent (for example, poppy and fireweed), and in some plants the seeds are thrown out of them with force (for example, violets).

Spread by water

Substances such as proteins, starch, sugars, fatty oils, some vitamins, etc. accumulate in the cells of the ovary wall. Only a few

fruits and seeds are specially adapted for dispersal by water. They contain air cavities that hold them on the surface of the water.

Rice. 3. Fruits spread by water

The coconut is a drupe with a fibrous mesocarp and numerous air-bearing cavities. In the water lily, the seed is equipped with a spongy shell derived from the stalk of the ovule.

Random distribution

The division of seeds and fruits into categories depending on their mode of distribution is not strict. In many cases, the element of chance plays a large role, and a given fruit or seed can spread in two of these three ways, or even in all three. One of the main factors in accidental spread is humans; seeds may cling or stick to his clothing, etc., or be transported with various loads on vehicles. Contamination of grain crops with weed seeds is a common phenomenon observed throughout to the globe. Nuts hidden in reserve by rodents can remain and germinate next spring. Floods, hurricanes, etc. can carry seeds further than usual.

Sexual reproduction in seed plants, which include flowering and gymnosperms, is carried out using seeds. In this case, it is usually important that the seeds are at a sufficiently distant distance from the parent plant. In this case, there is a greater chance that young plants will not have to compete for light and water, both among themselves and with the adult plant.

Angiosperms (aka flowering plants) in the process of evolution flora solved the problem of seed distribution most successfully. They “invented” such an organ as the fetus.

The fruits serve as an adaptation to a particular method of seed dispersal. In fact, most often the fruits spread, and the seeds along with them. Since there are many ways to distribute fruits, there are many varieties of fruits. The main methods of dispersal of fruits and seeds are as follows:

With with the help of the wind,

animals (including birds and humans),

self-spreading,

using water.

The fruits of plants that are distributed by the wind have special adaptations that increase their area, but do not increase their mass. These are various fluffy hairs (for example, poplar and dandelion fruits) or wing-shaped outgrowths (like maple fruits). Thanks to such formations, the seeds float in the air for a long time, and the wind carries them further and further from the parent plant.

In the steppe and semi-desert, plants often dry out and the wind breaks them off at the root. Rolled by the wind, dried plants scatter their seeds throughout the area. Such “tumbleweed” plants, one might say, do not even need fruits to spread their seeds, since the plant itself spreads them with the help of the wind.

Seeds of aquatic and semi-aquatic plants are spread with the help of water. The fruits of such plants do not drown, but are carried away by the current (for example, alder growing along the banks). Moreover, these are not necessarily small fruits. U coconut tree They are large, but light, so they don’t sink.

Adaptations of plant fruits to distribution by animals are more diverse. After all, animals, birds and humans can distribute fruits and seeds in different ways.

The fruits of some angiosperms are adapted to cling to animal fur. If, for example, an animal or the person will pass next to a burdock, then several prickly fruits will get caught on it. Sooner or later the animal will drop them, but the burdock seeds will already be relatively far from the original place. In addition to the burdock, an example of a plant with fruit-hooks is the succession. Its fruits are of the achene type. However, these achenes have small spines covered with teeth.

Juicy fruits allow plants to spread their seeds with the help of animals and birds that eat these fruits. But how do they spread them if the fruit and seeds along with it are eaten and digested by an animal? The fact is that mainly the juicy part of the pericarp of the fruit is digested, but the seeds are not. They come out of the animal's digestive tract. The seeds end up far from the parent plant and are surrounded by droppings, which, as you know, are a good fertilizer. Therefore, the juicy fruit can be considered one of the most successful achievements in the evolution of living nature.

Humans played a significant role in the dissemination of seeds. Thus, the fruits and seeds of many plants were accidentally or intentionally introduced to other continents, where they were able to take root. As a result, we can now, for example, observe how plants characteristic of Africa grow in America, and plants native to America grow in Africa.

There is an option for spreading seeds using scattering, or rather self-spreading. Of course, this is not the most effective method, since the seeds are still close to the mother plant. However, this method is often observed in nature. Typically, seed dispersal is typical for fruits of the pod, bean and capsule types. When a bean or pod dries out, its flaps curl into different sides, and the fruit cracks. Seeds fly out of it with little force. This is how peas, acacia and other legumes spread their seeds.

A fruit capsule (for example, a poppy) sways in the wind, and seeds fall out from it.

However, self-spreading is not limited to dry seeds. For example, a plant called squirting cucumber the seeds fly out juicy fruit. Mucus accumulates in it, which under pressure is thrown out along with the seeds.

>>Distribution of fruits and seeds

§ 4. Distribution of fruits and seeds

Lecture. Distribution of fruits and seeds.

One of the reasons for the huge diversity of seeds and fruits is various adaptations to their distribution.

Since the vast majority of plants lead an attached lifestyle, they are all forced to spread in space and time by rudiments - diasporas.

The process of spreading plant diaspores is dissemination (Latin disseminare - to disperse, spread).

Dissemination is necessary:

to preserve and expand the species' range;

as an avoidance option extreme conditions and periods of the year (waiting them out in an embryonic, dormant state);

to prevent unwanted inbreeding, enhance gene recombination, and => to preserve heterozygous heterotic individuals;

to maintain a more or less constant composition of phytocenoses.

From a theoretical point of view, the study of dissemination methods makes it possible to reveal the peculiarities of the biology of specific species, the ways of formation plant communities and vegetation cover.

From a practical point of view -

1) to study the possibilities of natural restoration of forests after fires, deforestation and other impacts.

2) in agricultural practice, knowledge of the distribution characteristics of weed species seeds helps reduce their numbers to a minimum.

The main methods of dispersal of fruits and seeds

(old textbook pp. 428 – 430).

To denote individual methods of plant dispersal, terms are used that are based on the root “choreo” - spreading, dispersing.

Dissemination of fruits and seeds

Autochory Allochory

Barochoria

Automechanochory Anemochory Hydrochoria

Geocarpy (by wind) (by water)

Zoochory Anthropochory

(animals) (humans)

1. Autochory– dispersal of fruits and seeds independently, without the participation of any external factors.

Autochory is carried out in 3 forms:

Barochoria– spontaneous fall of mature diaspores under their own weight ( weeds, palm trees, a number of Asteraceae with massive fruits and seeds, etc.).

Automechanochory– active scattering of seeds when opening a mature fruit (legume fruit valves – beans etc.; touch-me-not– strong osmotic pressure in the cells; when you touch a ripe fruit, the capsule opens with force and the seeds are scattered; mad cucumber– when the fetus ripens, there is an increase in pressure in the internal tissues and when it falls or external influence– the juicy pulp along with the seeds shoots out with force.

Geocarpy– self-ripening of fruits in the soil. In a number of violets and peanuts, after fertilization, thanks to the geotropic movements of the stalks, the ovaries are buried in the soil, where the growth and ripening of the fruits occurs.

Plants with autochorous fruits make up 20–30% of all flowering plants.

2. Allochory(Greek allos - other) - the spread of diasporas with the help of external factors (wind, water, animals, humans).

1. Anemochory– distribution of plant diaspores by air currents and wind.

Wind is the most common factor, but not always effective.

The bulk of seeds and fruits are carried through the air. Some spread by moving along the snow crust like a buer (pine seeds), some spread along the surface of the water (reed fruits), a number of tumbleweed plants are carried by the wind along the surface of the earth and at the same time scatter their seeds.

According to the methods of wind transfer, 3 groups of anemochorous plants are distinguished.

1 group. Plants with hovering seeds (hovering involves a long flight of seeds in the air), which is ensured by:

Low seed weight (for example, dusty seeds of wintergreen and orchids);

Special parachutes, hairs and tufts-papuses (in Asteraceae and willows), which provide:

Long flight of a seed or fruit;

The reduction of these seeds and fruits is ensured by the hygroscopicity of parachutes, hairs and crests.

2nd group. Plants with gliding seeds (for example, maple, ash, birch, elm). As a rule, such plants have fruits with outgrowths and are called - lionfish

. They fly along a descending trajectory, since they are heavier than floating fruits and are carried over shorter distances. 3rd group.

Plants with aerial fruits - airships (for example, desert legumes have light swollen fruits, carried by the wind like airships, partly through the air, and partly along the surface of sand, water, etc.). (Juzgun, strawberry clover). 2. Hydrochoria

- propagation of plant diaspores using water.

Diaspores of hydrochoric plants have adaptations that prevent wetting by water and => for their seeds and fruits they are characterized by:

Non-wetting (waxy layer, dense pubescence);

Hydrochoria is characteristic of hydrophytes, plants of sea coasts and river valleys (water lily, egg capsule, pondweed, coconut palm, burr). The most effective in terms of range is the distribution of seeds and fruits by sea currents.

3. Zoochoria– distribution of diasporas by animals.

There are endzoochory, epizoochory and synzoochory.

Endzoochory- seed dispersal when animals eat juicy fruits. The seeds pass intact through the digestive tract and are discarded in excrement. IN temperate latitudes

This method of seed dispersal is very typical for birds that eat bright, juicy, nutritious fruits of viburnum, rowan, bird cherry, and hawthorn, adapted for these purposes. The seeds of such plants often have a hard, stony seed coat. Epizoochory

– passive spread of diaspores on the animal’s body. Diaspores have special devices (trailers, spines, adhesive substances - string, Velcro, burdock) or they are very small and spread on feathers and paws, sticking to them with dirt (for example, plantain). Sinzoochory – active distribution associated with food storage. Diaspores equipped with special nutritional appendages - arillus (in corydalis, scilla, violets, castor beans, celandine) are taken away by ants - myrmecochory , or nut-shaped diaspores

4 . (in Siberian pine, oak, beech, hazel) are spread (unwittingly) by rodents (squirrels, mice, chipmunks) or birds (jays, nutcrackers), which make storerooms, which are then forgotten, not found and => thanks to them, forest restoration occurs in clearings and fires. Anthropochory

– distribution of plant diaspores associated with human activities. Anthropochory may be deliberate (transportation, sowing, placement of seeds of cultivated plants) and indirect (through irrigation water , transport transportation, accidentally together with others cultivated plants

(in Siberian pine, oak, beech, hazel) are spread (unwittingly) by rodents (squirrels, mice, chipmunks) or birds (jays, nutcrackers), which make storerooms, which are then forgotten, not found and => thanks to them, forest restoration occurs in clearings and fires.

and forage, with livestock). There are 3 forms of anthropochory.

Agestochoria Ergasiochoria

Speirochoria Agestochoria

– dispersal of plants by vehicles (does not depend on the dispersal adaptations of transported seeds and fruits). Intentional agestochory

– import of cultivated plants from other natural zones and continents (for us this is primarily the import of cultivated plants from America - potatoes, corn, tomatoes, sunflowers, etc.). Unintentional agestochory – spread of diasporas adventitious – plants along with other cargo (for example, in our region, along with wool from Siberia, an adventitious plant - hemp-leaved nettle) was brought along with it.

Agestochory is characterized by a long range and speed of spread.

Thus, many weeds were brought to America from Eurasia: field thistle, wild oat, great plantain - “the white man's trace”, and quarantine weeds - ragweed, cyclachena, etc. - were brought to Europe from America.

First, agestochorous plants colonize strips along railways, highways, and the territory of river ports, and then spread to the surrounding areas.

Speirochoria– distribution of plant diaspores by sowing them. => Characterized by a high degree of specialization of weed diaspores. Speirochoria led to the selection of specific weeds of the most ancient crops (wheat, rice, flax, millet, buckwheat) and the development of a number of adaptations in weeds, due to which their seeds can hardly be distinguished from the seeds of cultivated plants (the phenomenon of mimicry).

The fruits-caryopsis of oats and the wild oat weed are very similar, the fruits of buckwheat and the weed Tatary buckwheat, the caryopsis of rye and wheat, etc.

Ergasiochoria– spread of plant diaspores by agricultural tools and machines during soil cultivation.

Ergasiochoria is characteristic of weeds and a number of hay plants and contributes to the spread of diasporas within cultivated lands.

Thus, human labor activity creates great opportunities for seed dispersal.

In terms of efficiency and range, all methods are equivalent.

In terms of mass, anemo- and zoochoria are of greatest importance.

The dispersal of plants always occurs in space and time.

One of important properties fruits and seeds - dispersal of plants to new territories. Fruits and seeds are distributed through air and water, as well as with the help of animals and humans. Some plants have developed special adaptations to self-spreading seeds Plants impatiens, caragana (“yellow acacia”), “mad cucumber” (Fig. 165) seem to shoot their seeds. Such plants are called ballistas(from the Latin “ballista” - a throwing machine). In impatiens (Fig. 166) and caragana, the seeds scatter when the fruit leaves crack and curl. The “mad cucumber” accumulates mucus in the ripening fruits. As soon as an animal or person touches the fruit, sticky mucus along with seeds is released into it under great pressure.

Rice. 165."Squirting cucumber" Rice. 166. Impatiens fruits

Dispersal of fruits and seeds by air. On the single-seeded fruits of many trees (birch, maple, ash) wings are formed, and on the single-seeded fruits of dandelion (Fig. 167), mother and stepmothers, thistle - fluffy parachutes. With their help, achenes can fly tens and even hundreds of meters in the wind. Small seeds with fluffy tufts spread in the same way from poplar, willow, and fireweed. Rice. 167. Seeds and fruits dispersed by the wind.

Poppy, henbane and some other plants bend down to the ground during a gust of wind, and then straighten up with force and scatter seeds through the holes of the boxes (Fig. 167).

Dispersal of fruits and seeds using water. In plants growing in bodies of water or along their banks (water lilies, arrowheads, chastuhas, pondweeds), fruits and seeds are usually distributed through the water. They are not wetted by water and do not sink, thanks to the existing outgrowths or air cavities. In some plants, the fruits can float for several weeks or even months (arrowhead, alder, sedge, vekh) (Fig. 168). Coconut palm nuts travel great distances through salty sea water.

Rice. 168. Seeds and fruits distributed by water The fruits of some plants, which do not have adaptations to float on water, can be distributed by rain streams.

Distribution of fruits and seeds by animals. Many birds and animals feed on the juicy fruits of rowan, viburnum, cherry, and raspberry (Fig. 169). In their digestive organs, the pulp of the fruit is digested, and the seeds, protected by a dense peel, are removed outward along with droppings and scattered in the surrounding space.

Rice. 169. Fruits distributed by animals Some birds (jays) and animals (squirrels, mice, chipmunks) feed on large dry fruits (nuts and acorns) and store them for the winter. When dragging dry fruits to storerooms, animals often lose them along the way and often later do not find their supplies.

Ants play a significant role in seed dispersal. In ungulates, violets, and celandine, the seeds have succulent appendages (Fig. 170). Collecting ants carry such seeds into the anthill, but often lose them along the way.

Rice. 170. Seeds distributed by ants Some plants have fruits and seeds that have a variety of attachments. They cling to the fur of animals and they involuntarily carry them over various distances. In this way, the fruits of the string, gravilata and prickly infructescences of burdock are distributed (Fig. 169).

Small plantain seeds can mucus and stick to the soles of the feet of animals and humans. The seeds of some plants are spread along with silt, particles of damp soil that stick to the animals' bodies.

Often a person becomes an unwitting carrier of fruits and seeds.

As a result of economic activity, people often sow weeds along with cultivated plants. In addition, some fruits and seeds can travel by transport.

Biological role of fruit and seed distribution.

Have you paid attention to how the plants grow around you and why there is no zonality or striation in their arrangement (for example, in one place there is a strip of poplars, a little further there is a strip of dandelions, behind them there are rose hips or lilacs). We see that all the vegetation around us is “mixed”, a kind of vinaigrette. What contributes to this? How can plant seeds travel? Theoretical basis The vitality and diversity of the plant world depend on the ability of species to disperse. The parent plant is attached to one place by its roots all its life, therefore, its offspring must find another. This task of developing new space was entrusted to seeds and fruits. First, the pollen must land on the pistil of a flower of the same species, i.e. pollination must occur. Secondly, the pollen tube must reach the ovule, where the nuclei of the male and female gametes merge. Finally, the mature seed has to leave the parent plant. The probability that the seed will germinate and the seedling will successfully take root in a new place is an insignificant fraction of a percent, so plants are forced to rely on the law large numbers and disperse as many seeds as possible. The latter parameter is generally proportional to their chances of survival. Very rarely, seeds germinate on the plant itself, as is observed in the so-called viviparous representatives of mangrove forests. Much more often, seeds or fruits with seeds enclosed in them completely lose connection with the mother plant, and begin to live independently somewhere else. Often seeds and fruits fall close to the mother plant and germinate here, giving rise to new plants. But more often than not, animals, wind or water carry them to new places, where, if conditions are suitable, they can germinate. This is how resettlement occurs - a necessary stage in seed propagation. Due to settlement, there is a gradual expansion of the area occupied by a given population or even species. It is thanks to this that many species could capture those huge areas which they occupy. But the importance of resettlement does not end there. As Charles Darwin wrote, it facilitates cross-pollination. In addition, dispersal allows the species to occupy a variety of habitats, which is of great importance for the process of formation of new populations and races. Thanks to resettlement, the composition of plant communities is enriched and thereby the diversity of life increases. Finally, thanks to resettlement, new territories freed from under water after a fire, a volcanic eruption, as well as newly emerged islands are being developed. Fruits and seeds dispersed by the wind. In some plants, light fruits or seeds are carried by the wind, for example, dust-like seeds of orchids or fruits with wings, which are sometimes formed by parts of the perianth, like maple, for example. In many representatives of the Asteraceae, for example, in dandelions, a fluffy bundle of villi, similar to a parachute, helps the light fruit to float in the air. In some plants, the wing or tuft of hairs bears not the fruit, but the seed itself; in toadflax, in particular, the seeds are winged, and in fireweed, they have a tuft. In willows and poplars, the entire seed coat is covered, as it were, with felt. In tumbleweed species, the entire plant (or part of it) is driven along the ground by the wind, scattering the seeds. Fruits and seeds that spread by scattering. Some plants shoot out their seeds. Thus, in impatiens they are thrown some distance away by the suddenly separating flaps of the capsules. In gamamelis, when the fruit dries, the endocarp contracts, scattering the seeds with such force that they can fly up to 15 m. In contrast to these active methods of dispersal, the seeds and fruits of many plants simply fall to the ground and then move more or less passively, in particular periodically active agents, for example, floods. Fruits and seeds dispersed by water. The fruits and seeds of many species, especially those growing in or near bodies of water, are capable of floating. This is explained by the presence in them of either special air chambers or loose tissues with air-filled intercellular spaces. Some fruits are specially adapted to be distributed by ocean currents, such as the coconut palm; that is why it quickly populates almost all of the atolls that have emerged relatively recently in the Pacific Ocean. Rain, too, is a common agent for the dispersal of fruits and seeds; it is especially important for plants growing on the slopes of mountains and hills. Fruits and seeds distributed by animals. The sweet and often brightly colored fleshy fruits are undoubtedly evidence of the coevolution of animals and plants. In most cases, those in which a significant part of the pericarp is fleshy (for example, plums, raspberries, dogwoods, grapes) are eaten by vertebrates (usually mammals or birds), and then the seeds they contain, passing through the digestive tract or regurgitated by animals, end up on long distance from the place where they were swallowed. Sometimes incomplete digestion, which softens the seed coat, promotes seed germination. As they ripen, the fleshy fruits undergo a number of characteristic changes under the influence of the hormone ethylene. The sugar content in them increases, the tissues soften due to the destruction of pectin substances, and the greenish, inconspicuous color of the leaves gives way to bright red, yellow, blue or black. The seeds of some plants, especially in the tropics, have brightly colored fleshy appendages. Their juiciness and color, like fruits, contribute to the spread of seeds by vertebrates. Often the green or camouflage color of unripe fruits to a certain extent protects them from premature consumption by animals. However, they can taste unpleasant, like very sour unripe cherries, which also repels animals. By changing the color when the fruits ripen, the plant “signals” that they are edible, that is, that the seeds are ripe and ready to spread. It is no coincidence that the color red predominates at this time. Thanks to it, the fruits are invisible to insects - apparently they merge with the green background of the leaves. These animals are too small to effectively disperse the seeds of fleshy fruits, and it is not beneficial for the plant to attract them. At the same time, red fruits are clearly visible to vertebrates, which, by eating them, transport mature seeds over long distances. The fruits or seeds of many angiosperms spread by attaching themselves to the fur or feathers of animals, and are equipped with hooks, barbs, spines, bristles or adhesive coverings for this purpose. Features of the distribution of seeds and fruits in some plants The coconut palm has the largest seeds in the plant world. They are able to swim indefinitely in the oceans until the waves throw them onto soft coastal sand, where the competition of seedlings with other plants will be much weaker than in the thicket of the forest. As a result, the chances of each of them taking root are quite high, and one mature palm tree, without risk to the species, usually produces only a few dozen seeds per year. Orchids, on the other hand, have the smallest seeds in the world; in tropical forests they are carried by weak air currents among high crowns and germinate in moist cracks in the bark on tree branches. The situation is complicated by the fact that on these branches they need to find a special type of fungus, without which germination is impossible: small orchid seeds do not contain nutrient reserves and in the first stages of seedling development they receive them from the fungus. It is not surprising that one fruit of a miniature orchid contains several thousand of these seeds. Angiosperms are not limited to producing a variety of seeds through fertilization: the ovaries, and sometimes other parts of flowers, develop into unique seed-containing structures called fruits. The ovary can become a green bean that protects the seeds until they ripen, turn into a durable coconut capable of making long sea voyages, juicy apple, which an animal will eat in a secluded place, using the pulp, but not the seeds. Berries and drupes – favorite treat birds: the seeds of these fruits are not digested in their intestines and end up in the soil along with excrement, sometimes many kilometers from the parent plant. The fruits are winged and fluffy, and the shape of their volatile-increasing appendages is much more varied than that of pine seeds. The wing of the ash fruit resembles an oar, that of the elm it resembles the brim of a hat, that of the maple the paired fruits - biptera - resemble soaring birds, and that of the ailanthus fruit's wings are twisted at an angle to each other, forming, as it were, a propeller. These devices allow flowering plants to use seeds very effectively for dispersal. external factors. However, some types of outside help don't count. Thus, the fruits of impatiens are a kind of catapult. Geraniums also use a similar mechanism. Inside their long fruit there is a rod, to which four, for the time being, straight and connected valves are attached - they are held firmly on top, weakly on bottom. When ripe, the lower ends of the valves break away from the base, curl sharply towards the top of the stem and scatter the seeds. In the ceanothus shrub, well known in America, the ovary turns into a berry, similar in structure to a time bomb. The pressure of the juice inside is so high that after ripening, a warm ray of sunlight is enough for its seeds to scatter in all directions like living shrapnel. The boxes of ordinary violets, when dry, burst and scatter seeds around them. Witch hazel fruits operate on the principle of a howitzer: to make the seeds fall farther, they shoot them at a large angle to the horizon. In Virginia knotweed, in the place where the seeds are attached to the plant, a spring-like structure is formed that discards mature seeds. In oxalis, the fruit shells first swell, then crack and shrink so sharply that the seeds fly out through the cracks. Arceutobium is tiny, using hydraulic pressure inside the berries to push the seeds out of them like miniature torpedoes.