Banded tube

Banded tubes are a type of phytoclast consisting of micrometre-scale tubes with a banded internal ornamentation, and known from terrestrial/freshwater settings from the early Silurian onwards.

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