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Contact-Poisonous Plants of the WorldThe result is often immediate burning sensation of the skin. The best known representative of this kind of plants is the Stinging Nettle. Its closely related species are native to all parts of the world. Most mechanically-chemically acting plants belong to the botanical families Urticaceae and Euphorbiaceae, some of them being much more powerful than the Stinging Nettle. Under an electron microscope, fragile hollow needles become visible with nettle cells at their bases, filled with liquid poison. When touched, the needles break off, leaving oblique tips which can enter the human skin like syringes and release the poison. Electron-microscope image of a stinging hair of Urtica dioica. Image: Y. Sell. Another powerful principle, the allergizing principle, is found mainly in members of one botanical family called the Anacardiaceae. Infamous examples are the Toxicodendron species native to North America. The first encounter with one of them usually does not have any noticable consequences. But it allergizes the victim, and any subsequent contact can cause gradually more severe skin irritation ...» |
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