Final answer:
A rhizoid is a filament of cells that anchors bryophytes to the ground. It provides anchorage for the plant and is found in mosses, liverworts, and hornworts.
Step-by-step explanation:
A rhizoid is a long tubular single cell or filament of cells that anchors bryophytes to the ground. It is a thin filament made up of individual cells that provides anchorage for the plant to the substrate. Unlike roots, rhizoids primarily serve an anchorage role and perform little absorption. They are found in mosses, liverworts, and hornworts. Rhizoids play an important role in stabilizing the plant and providing support.