Banded tubes are a type of phytoclast consisting of micrometre-scale tubes with a banded internal ornamentation, and known from terrestrial/freshwater^[1] settings from the Early Silurian onwards.^[2]

The bands on the walls were an early improvisation to aid the easy flow of water,^[3] and served as tracheids, although they are not equivalent in their construction. Banded tubes were lignified,^[4] giving them a more rigid structure than hydroids, allowing them to cope with higher levels of water pressure.^[5]

Banded tubes have a markedly different ultrastructure from plant tracheids, and display a wide variety of wall structures, which implies that they were produced by a variety of different organisms, or perhaps were widely variable within a single nematophyte-like organism.^[1]

Proposed functions include water transport, feeding (cf. fungal hyphae), and anchorage (cf. rhizoids).^[1]

Some banded tubes can be assigned to genera such as Nematoplexus and Nematasketum, in the latter, they occur in bundles alongside other tubes; Nematasketum is probably fungal.^[6]