Cloud ear fungus (Auricularia polytricha, syn. Hirneola polytricha) is an edible jelly fungus. It is gray-brown in color and often used in Asian cooking. In Chinese, it is known as 云耳 (pinyin: yún ěr, lit. "cloud ear"), 毛木耳 (pinyin: máo mù ěr, lit. "hairy wood ear"), or 木耳 (pinyin: mù ěr, lit. "wood ear" or "tree ear"), and in Japanese it is called arage kikurage (キクラゲ, lit. "tree jellyfish"). It is also known as black fungus, black Chinese fungus (or mushroom), wood ear fungus, wood fungus, ear fungus, or tree ear fungus, an allusion to its rubbery ear-shaped growth.
The fungus grows in frilly masses on dead wood. It is a dark brown color but somewhat translucent. It is usually sold dried and needs to be soaked before use. While almost tasteless, it is prized for its slightly crunchy texture and supposed medicinal properties, including its newly discovered anticoagulant properties. Of note, the slight crunchiness persists despite most cooking processes.
Auricularia auricula-judae, a closely related species, is also used in Asian cooking.
Snow fungus, another edible fungus which is white in color, is a separate species, Tremella fuciformis.