Definition of thallus in English:



  • A plant body that is not differentiated into stem and leaves and lacks true roots and a vascular system. Thalli are typical of algae, fungi, lichens, and some liverworts.

    • ‘Filaments are typically tightly twisted and bundled, but may become separated in the middle part of the thallus.’
    • ‘Oomycetes resemble fungi in the form of their thalli, ecology, and the plant parasitic ability of some species and are traditionally studied by mycologists.’
    • ‘Ceratopteris spores, like fucoid zygotes, divide unequally to produce a small rhizoid cell and a larger cell that develops into the thallus.’
    • ‘The thallus and rhizoid can be distinguished by their different patterns of cell division.’
    • ‘Some causal relationships between morphology and hydrodynamic performance have been established for macroalgae, through theoretical studies and hydrodynamic comparisons of differently exposed thalli.’


Early 19th century: from Greek thallos ‘green shoot’, from thallein ‘to bloom’.