thallus noun. ['Ɵalǝs] Pl. -lli [-lʌɪ, -li:]. E19.
[Greek thallos green shoot, from thallein to bloom.]
Botany. A plant body (as in algae, fungi, lichens, and some liverworts) not differentiated into stem and leaves, lacking true roots or a vascular system, and freq. flattened and ribbon-like.

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