Trees, Truffles, and Mycorrhizae: Beneficial Fungi

Updated on April 4, 2018
AliciaC profile image

Linda Crampton is a writer and teacher with an honors degree in biology. She loves to study nature and write about animals and plants.

White truffles from Croatia; truffles are made by fungi that form mycorrhizae on the roots of certain types of trees
White truffles from Croatia; truffles are made by fungi that form mycorrhizae on the roots of certain types of trees | Source

Useful and Interesting Organisms

Fungi are interesting organisms that help us in many ways. They make tasty and nutritious food for us, decompose the bodies of dead organisms and recycle their nutrients, and produce medications to treat diseases. Some fungi live on or in plant roots in an association known as a mycorrhiza, which benefits both organisms. Biologists say that plants which normally have mycorrhizae either couldn't grow without their fungal companions or would grow much less successfully.

Researchers have discovered that the mycorrhizal fungi in a habitat are often attached to more than plant and form a communication network between them. In forests, the network is sometimes referred to as the "Wood-Wide Web".

Truffles are flavourful gourmet mushrooms and are another beneficial fungal product. A truffle is a reproductive structure of a mycorrhizal fungus belonging to the genus Tuber. Chanterelles, morels, porcini mushrooms (or boletes), and matsutake mushrooms also develop from mycorrhizal fungi.

Hyphae of a fungus growing on top of mushrooms
Hyphae of a fungus growing on top of mushrooms | Source

The plural form of mycorrhiza is either mycorrhizae or mycorrrhizas. Many types of plants have mycorrhizae, including trees. The most common kinds of Christmas trees—fir, Douglas fir, spruce, and pine trees—grow in association with mycorrhizal fungi. Cacao trees, which give us the cocoa used to make chocolate, also have mycorrhizae.

The Structure and Life of a Fungus

A fungus consists of thread-like structures called hyphae. The hyphae branch as they grow to form a tangled web known as a mycelium. The mycelium of a fungus produces reproductive structures called fruiting bodies, which make spores. Once a spore is released into the environment it can produce new hyphae. Fruiting bodies may be small structures, but in some cases—such as mushrooms—they are large and noticeable.

The hyphae of a fungus release digestive enzymes into the material in which they're growing, or the substrate. These enzymes break the substrate down, producing molecules that are absorbed by the fungus and used as nutrients. Fungi aren't plants. They don't contain chlorophyll and can't make their own food by photosynthesis.

Although a mycorrhizal fungus gets its food from a plant's roots, it doesn't destroy the plant. The two organisms live as partners, with each giving the other something that it lacks or has difficulty obtaining.

The mycelium or body of a mold (a type of fungus) as seen under a microscope
The mycelium or body of a mold (a type of fungus) as seen under a microscope | Source

Mycorrhizae and Plants: Symbiosis and Mutualism

It's estimated that between sixty-five and ninety percent of vascular land plants (those with water and food conduction vessels) have mycorrhizae. The estimated percentage varies according to the reference source. The relationship between the fungus and the plant in a mycorrhiza is referred to as symbiosis because it involves two different organisms living together. It's also classified as mutualism, since both organisms benefit from the relationship.

The presence of the fungus greatly increases the surface area of the roots, enabling more water and nutrients to be absorbed. The fungus absorbs important chemicals that the plant needs, including phosphorus and nitrogen. The nutrients are then absorbed by the root cells. Research has shown that mycorrhizal fungi increase the concentration of phosphorus in their host by up to forty percent. The fungus benefits from its association with the plant by having access to sugars stored in the root, which it uses for food.

Pine trees such as this one have mycorrhizae.
Pine trees such as this one have mycorrhizae. | Source

Mycology is a division of biology that deals with the study of fungi. A scientist who studies fungi is known as a mycologist.

Traditional Classification of Mycorrhizae

Traditionally, mycorrhizae have been classified in three categories, as described below.

Ectomycorrhizae develop mainly on the surface of plant roots. The fungus forms a mycelial net over the plant's rootlets, or the fine divisions of the roots. The net is called a fungal sheath or a mantle. The mycelial net sends hyphae into the outer layers of the root. These hyphae extend through the spaces between the outer root cells but generally don't enter the cells. The network of intercellular hyphae is known as a Hartig net. It was named after Robert Hartig, a mycologist from the nineteenth century. Most trees have ectomycorrhizae.

Endomycorrhizae develop mainly or completely inside plant roots. There is usually no mantle around the outside of the roots. If one exists, it's generally made of only a few hyphae. The hyphae of the fungus are located inside the outer root cells and may or may not be located between the cells as well.

Ectendomycorrhizae have characteristics of both ectomycorrhizae and endomycorrhizae and are found in a few types of trees, including pine and spruce.

Root tips covered with the white hyphae of Amanita, a mycorrhizal fungus
Root tips covered with the white hyphae of Amanita, a mycorrhizal fungus | Source

A Modern Classification System

The three-category system of mycorrhizae classification described above is considered to be too simplistic by many mycologists today. A more modern system breaks the endomycorrhizae up into five categories. The ectomycorrhizae and ectendomycorrhizae categories are retained, creating a total of seven categories. The five new categories are listed below.

  • Arbuscular (the most common type of mycorrhiza): the hyphae penetrate root cells and grow into a form that looks like a tiny tree (an arbuscule); the hyphae of some fungi in this category also form bladder-like structures in cells called vesicles
  • Ericoid: found in certain members of the order Ericales, including heath or heather (genus Erica), ling or heather (genus Calluna), and bilberry (genus Vaccinium)
  • Monotropoid: found in members of the family Monotropaceae within the order Ericales; members of this family lack chlorophyll
  • Arbutoid: found in some members of the order Ericales
  • Orchid: found in orchids in at least one stage of their life

The Wood-Wide Web in Forests

Researchers have found that some of the ectomycorrhizal hyphae around the root of one plant travel to the root of a neighbouring plant and surround and enter it, too. In addition, one plant may form mycorrhizae with several fungi. In a community of plants, such as a forest, a network of plants connected by hyphae is formed.

A plant-fungus network based on mycorrhizae is referred to as a wood-wide web or a common mycelial network (CMN). Scientists have discovered that the fungal connection allows chemicals to be transferred from one plant to another instead of only between a single plant and its root fungi. The CMN is still being explored, but some scientists are already saying that a field of plants or a forest of trees connected by mycorrhizae could be viewed as a superorganism instead of a collection of individuals.

It's already known that in at least some plants a chemical can transmit a message from one individual to another through the air. It will be very exciting to discover the types of information that plants transfer via chemicals travelling through mycorrhizae. Some people are jumping to as yet unsubstantiated conclusions about the extent of the transferred information, however.

Investigating the Wood-Wide Web

When some plants are injured by insects, they release airborne chemicals that travel to nearby plants. The chemicals stimulate the plants to defend themselves in some way, such as by producing substances that repel the insects or attract predators of the insect.

Plant Communication via Mycorrhizae

For some time scientists have suspected that plants can communicate through their connected mycorrhizae. Now exciting research is gradually showing that this is the case. For example, researchers have found that when broad bean plants are attacked by aphids, they can "warn" other plants about the danger through mycorrhizae.

In an interesting experiment, scientists allowed some bean plants to form mycorrhizal connections with each other but prevented others from doing so. They covered the plants with bags so that no plant chemicals could enter the air.

The scientists placed aphids on some of the bean plants. These plants produced chemicals to repel the aphids. If a plant with aphids was connected to ones without aphids via mycorrhizae, the connected plants also made chemicals to prevent the aphid attack. If the plants weren't connected, only the plant with the aphids mounted a chemical attack. The other plants apparently received no signal from the injured plant and made no defensive chemicals.

The pea aphid: adults and nymphs (immature forms of an aphid)
The pea aphid: adults and nymphs (immature forms of an aphid) | Source

What Are Truffles?

A truffle is the mushroom of an ectomycorrhizal fungus. Like other mushrooms, it contains spores. However, truffles are formed underground. Their spores are distributed when animals dig up the mushroom to eat it. True truffles belong to the genus Tuber, but there are similar fungi in other genera.

The mycelium of a truffle forms mycorrhizae with the roots of several types of trees, including hazel, birch, poplar, beech, oak, and pine trees. Truffles can be found in several parts of the world, including North America, but only certain species are eaten by humans. These are highly valued by some people.

Black truffles from Croatia
Black truffles from Croatia | Source

According to Guinness World Records, the largest truffle on record is an Alba white truffle weighing about 3.27 pounds. It was found in Italy on November 4th, 2014.

Gourmet Mushrooms

Truffles look very unimposing but have a flavour that many people love. They also have a strong aroma. Intact truffles can be very expensive, ranging from around a hundred dollars a pound for lesser known varieties to several thousands or even many thousands of dollars per pound for the most popular ones.

The two most famous truffles are the Alba white truffle (Tuber magnatum), named after the Italian city of Alba, and the Perigord black truffle (Tuber melanosporum), named after the Perigord region of France.

There is a burgeoning market for local truffles grown in North America. Some North American farmers have imported truffle spores from other countries, as have people in other parts of the world. A would-be truffle farmer needs patience, however. Seven to nine years are required after inoculation of a host plant with spores before the mushrooms are ready to harvest.

Truffles are served as shavings placed on food such as eggs, meat, chicken, fish, cheese, and salads. They are also chopped or grated and added to butter, stuffing, and sauces. Alba white truffles taste best when raw, while the flavour of Perigord black ones intensifies with heating. Truffle oil isn't a good substitute for the mushrooms because in general it's not made from truffles. The ingredients on a bottle of oil should be checked carefully before it's purchased.

A Truffle-Hunting Pig

Hunting for Truffles With Pigs and Dogs

Pigs and dogs are both used to find truffles. Female pigs are attracted to the aroma of the mushrooms because they contain a chemical which smells like the male pig's pheromone, or mating attractant.

Dogs can be trained to detect truffles and then indicate their presence. Some people prefer to use dogs in the hunt because the dogs are less likely to eat the mushrooms when they discover them. The Lagotto Romagnolo is a breed of dog known for its truffle-hunting ability. It's said to make a good pet as well, but since it was bred as a working dog it requires a lot of physical exercise as well as exercise for its brain.

Though animals can be very be helpful in finding truffles, some people hunt for the mushrooms by themselves. They do this by raking the soil in the area where the fungi are likely to be found.

A Lagotto Romagnolo Dog Searches for Truffles

Mycorrhizal Fungi and Plants: An Important Relationship

There is still a lot to learn about mycorrhizal fungi and their relationship with plants. It's an important area of study, since we are so dependent on plants and so many of them live in partnership with fungi. Research is showing that mycorrhizal fungi play an important role in maintaining plant health. Keeping plants healthy is important for our future and for the future of the planet.

References

  • Information about mycorrhizal fungi from the New York Botanical Garden
  • Facts about mycorrhizae from David Moore's World of Fungi (Dr. David Moore is a mycologist.)
  • Bücking, H., Mensah, J. A., & Fellbaum, C. R. (2016). Common mycorrhizal networks and their effect on the bargaining power of the fungal partner in the arbuscular mycorrhizal symbiosis. Communicative & Integrative Biology, 9(1), e1107684. http://doi.org/10.1080/19420889.2015.1107684
  • Communication in broad beans via mycorrhizae from the BBC (British Broadcasting Corporation)

Questions & Answers

    © 2013 Linda Crampton

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      • AliciaC profile image
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        Linda Crampton 2 years ago from British Columbia, Canada

        Thank you very much for the comment and the congratulations, RTalloni. Nature is certainly amazing!

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        RTalloni 2 years ago from the short journey

        What an amazing world of wonders that we live in! Thanks for a neat read and congrats on your Hub of the Day award on this engaging post.

      • AliciaC profile image
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        Linda Crampton 2 years ago from British Columbia, Canada

        Thank you very much for the comment, Au fait. I completely understand what you've said and I understand your frustration. I am grateful for every HOTD that I get, though. Like other writers, I want to feel that my writing has value. Some writers at HubPages get a huge number of comments on their hubs; some people have the knack for creating hubs that make a lot of money. Neither of these points is true for me, so I am happy whenever I see that I have a HOTD. As I say, though, I do appreciate your point of view.

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        C E Clark 2 years ago from North Texas

        Wow! Still another HOTD! Starting to look like every single one of your hubs is a HOTD or soon will be.

        Congratulations to you! The rest of us get a BIG FAT F it looks like. Meaning no disrespect. I love your hubs and you've written them superbly, but what is HP saying to everyone when they single out one person to get all the rewards? By all means, take all you can get. They may have a different bug in a different place tomorrow . . . :)

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        Linda Crampton 2 years ago from British Columbia, Canada

        Thank you very much, eilval. I appreciate your visit and the congratulations.

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        Eileen 2 years ago from Western Cape , South Africa

        Fascinating and informative hub. Congrats on HOTD !

      • AliciaC profile image
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        Linda Crampton 2 years ago from British Columbia, Canada

        Thanks for the congrats and the comment, Kristen!

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        Linda Crampton 2 years ago from British Columbia, Canada

        Thank you for the congratulations, ChitrangadaSharan! I appreciate your kind and interesting comment.

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        Linda Crampton 2 years ago from British Columbia, Canada

        Thank you very much, adevwriting!

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        Kristen Howe 2 years ago from Northeast Ohio

        Congrats Linda on another HOTD for this interesting hub!

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        Chitrangada Sharan 2 years ago from New Delhi, India

        Congratulations for HOTD!

        This is an excellent hub and very informative!

        The way Nature operates is so complex as well as interesting. We humans thoughtlessly spoil, burn and build over it without thinking twice of what we are destroying.

        Thank you for sharing this very important hub!

      • adevwriting profile image

        Arun Dev 2 years ago from United Countries of the World

        Interesting hub! Learned about truffles and pigs and dogs that can hunt for it. Congrats on another HOTD!

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        Linda Crampton 3 years ago from British Columbia, Canada

        Thank you for the comment and the votes, Mary. I appreciate your support so much!

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        Mary Hyatt 3 years ago from Florida

        I learn so much from your articles! I have a daughter who lives in Oregon, and she was just telling me she had a hamburger cooked in truffle oil. From what I have read, truffle oil is very healthy!

        I've never tasted it myself, but I'd like to. I enjoyed the videos you included.

        Voted UP, etc.

      • AliciaC profile image
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        Linda Crampton 3 years ago from British Columbia, Canada

        Thank you for the interesting comment, oceansnsunsets. It certainly sounds like your husband had a delicious meal!

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        Paula 3 years ago from The Midwest, USA

        Hi Alicia, I learned something new today about truffles and trees, their root systems, etc. Very interesting! My husband had an amazing meal the other week that included some truffles, and he said it was probably the best thing he has ever eaten. This is such an interesting topic, and I like learning more about it, so thank you for sharing it.

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Yes, truffle hunting does sound like an interesting job. Thanks for the visit and the comment, ologsinquito.

      • ologsinquito profile image

        ologsinquito 4 years ago from USA

        I've always found truffle hunting such an interesting occupation, with the dogs being used to sniff out these delicacies.

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Hi, Deb. Yes, symbiosis between fungi and plants is wonderful! As you say though, some fungi are poisonous. It's important to be careful!

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        Deb Hirt 4 years ago from Stillwater, OK

        Isn't symbiosis a wonderful thing? Be careful with that pine tree fungus. If you're around it too much, you WILL become sick.

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        Linda Crampton 4 years ago from British Columbia, Canada

        Hi, Eddy. Thanks for the comment and the vote. Have a great day, too!

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        Eiddwen 4 years ago from Wales

        Interesting and very useful Alicia. voting up and wishing you a great day.

        Eddy.

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        Linda Crampton 4 years ago from British Columbia, Canada

        Thank you, Mike! I appreciate your visit very much.

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        Mike Robbers 4 years ago from London

        Very well written and interesting Alicia!!

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Thank you very much for the comment, Dianna. Yes, chocolate truffles that could be harvested would be a wonderful food!

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        Dianna Mendez 4 years ago

        I only wish they came in chocolate. Your posts are always so interesting and I make it a habit to read them.

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Hi, epbooks. Strangely enough, I've just been to the store to buy mushrooms, too! Thank you for the visit and the comment.

      • epbooks profile image

        Elizabeth Parker 4 years ago from Las Vegas, NV

        Wow- a very informative hub. Just bought some mushrooms to cook, but I don't think I've ever had truffles!

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Thank you very much for the comment, Crafty. Truffle pigs are interesting animals! I would love to meet one.

      • CraftytotheCore profile image

        CraftytotheCore 4 years ago

        Your Hubs are so delightful to read. I just love the truffle hunting pig. How adorable is that! And to know there is so much good that this fungus does. Amazing.

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Hi, drbj. Thank you for the visit. As always, I appreciate your comment and your humor!

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        drbj and sherry 4 years ago from south Florida

        Fungi are fascinating organisms, Alicia, and you provided an exemplary introduction to this subject. Love that truffle-searching pig who decided to lie down and rest before embarking on its truffle hunt.

        I once dated a fungi - no, wait a minute, that was a fun guy Sorry, the debbil made me do it. :)

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Thank you for the visit, paydayreloan.

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        paydayreloan 4 years ago

        Thank very much

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Thank you so much for the comment, the votes and the share, Faith! As always, I appreciate your visit to my hub and your kind comment. Blessings to you.

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        Faith Reaper 4 years ago from southern USA

        Fascinating information here dear Alicia! You are always amazing me with your insightful and educational hub. That is awesome how the plants communicate with each other! Now, that is one huge truffle there, wow.

        Up and more and sharing

        Blessings, Faith Reaper

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Thank you for the comment, Pamela. Plants have some interesting features that some people are unaware of! They can be surprising organisms. I appreciate your vote.

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        Pamela Oglesby 4 years ago from United States

        I never knew plants communicated with each other to help protect themselves, and there were many other items I had not known as well. This is a very interesting hub. I would like to eat a truffle sometime. Voted up!

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Hi, EGamboa. Yes, exploring the taste of different types of truffles would be a fun activity if we could afford it!

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Thank you very much, Cynthia. Yes, humans can be very destructive. Our effects on the environment are very worrying.

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        Eileen Gamboa 4 years ago from West Palm Beach

        My bucket list: taste a truffle. (providing an end up with lots of do de o dough!)

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        CMHypno 4 years ago from Other Side of the Sun

        Fascinating hub as always Alicia. The way nature operates is so complex and interesting, yet we humans thoughtlessly slash, burn and build over it with no thoughts of what we could be destroying.

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Hi, Bill. Yes, I love the fall display of wild mushrooms! They have such an interesting variety of colors and appearances. Observing and photographing them gave me the idea for this hub. Thank you very much for the comment, Bill.

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        Bill Holland 4 years ago from Olympia, WA

        We live in a great part of the world for mushrooms, don't we? Great information as always, Alicia. I always learn something new from you and I appreciate it very much.

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Hi, MG Singh. Thank you for reading the article and for the comment.

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Thanks for the comment, DDE. I appreciate the votes!

      • AliciaC profile image
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        Linda Crampton 4 years ago from British Columbia, Canada

        Thank you for the visit and comment, Martin.

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        MG Singh 4 years ago from Singapore

        Very interesting and informative hub.

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        Devika Primić 4 years ago from Dubrovnik, Croatia

        Trees, Truffles and Mycorrhizae - Beneficial Fungi so interesting about truffles I had learned more here. Voted up, interesting useful, and a well informed hub.

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        Martin Kloess 4 years ago from San Francisco

        How interesting, Thank you for this.

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