ریسه

thumb|300x300px|Thallus of Pellia epiphylla Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entire body of a multicellular non-moving organism in which there is no organization of the tissues into organs. Many of these organisms were previously known as the thallophytes, a polyphyletic group of distantly related organisms. An organism or structure resembling a thallus is called thalloid, thalloidal, thallif