ˈthaləs noun
( plural thal·li -aˌlī ; or thalluses )
Etymology: New Latin, from Latin, young shoot, green stalk, from Greek thallos, from thallein to sprout — more at thalia
: a plant body that is characteristic of the thallophytes, that does not grow from an apical point, shows no differentiation into distinct tissue systems (as vascular tissue) or members (as stems, leaves, or roots) or is composed of members resembling and performing many of the functions of but not homologous with those of the higher plants, and that may be simple or branched, may consist of filaments or plates of cells, and may vary widely in form and size from microscopic one-celled plants to complex foliated or arborescent forms (as in some of the larger marine algae)