The New Student's Reference Work/Tracheid

Vertical section of pine wood, showing the pitted tracheids crossed by a pith ray.

Tracheid (tra′kē̇-ĭd) (in plants), a single cell with all the wall features of a trachea, but not uniting with others to form a vessel. It is more or less elongated and taper-pointed like a fiber. Tracheids form the characteristic soft and straight-grained wood of pines and other conifers. In these forms, as in all gymnosperms, the walls of the tracheids contain bordered pits, that is, pits which appear to have a double border about them. This type of pit is a constant feature in gymnosperms, so that the group may be recognized even by a single wood-fiber.