what is thallus

Thallus is a term used to describe the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. It is the plant-like vegetative body of algae, fungi, or mosses that lacks differentiation into distinct parts such as stem, leaves, and roots and does not grow. A thallus usually names the entire body of a multicellular non-moving organism in which there is no organization of the tissues into organs. Even though thalli do not have organized and distinct parts as do the vascular plants, they may have analogous structures that resemble their vascular "equivalents". For example, a kelp may have its thallus divided into three regions, including the holdfast (anchor), stipe (supports the blades), and the blades (for photosynthesis) . The thallus of a fungus is usually called a mycelium.