rhizoid

A threadlike outgrowth from a thallus, as seen, for example, in the gametophyte generation of mosses, liverworts, and ferns. Usually rhizoids serve to anchor the plant and absorb water and nutrients. In some algae, e.g. Ulva, they are incorporated into and strengthen the lamina. Mosses can be distinguished from liverworts by their multicellular, usually brownish rhizoids. In liverworts rhizoids are unicellular and more or less colourless, resembling the root hairs of higher plants. Compare root.