In cell biology a centriole is a cylindrical cell
structure composed mainly of a protein called tubulin that is found in mosteukaryotic cells. Centrioles are
absent from Pinophyta, flowering plants and most fungi and are only present in
the male gametes of charophytes, bryophytes, seedless vascular plants, Cycads, and Gingko. An associated pair of centrioles, surrounded by an
amorphous mass of dense material, called the pericentriolar
material, or PCM, makes up
a compound structure called a centrosome.