what is thallus
Definition of THALLUS. : a plant body that lacks differentiation into distinct parts (as stem, leaves, and roots), does not grow from an apical point, and is characteristic of organisms formerly classified as thallophytes.ADVERTISEMENT. a plant body that lacks differentiation into distinct parts (as stem, leaves, and roots), does not grow from an apical point, and is characteristic of organisms formerly classified as thallophytes. ADVERTISEMENT.