Tracheal synonyms

These spiracles, according to Hinds, are remarkable honeycomb-like structures, and perforations to the tracheal tubes have not been demonstrated.

The xylem parenchyma is often found in strands associated with the tracheal elements.

Tracheal system reduced or absent.

To admit of the free inflow and outflow of currents of water necessary for respiration, which is effected by means of filamentous abdominal tracheal gills, the two ends of the tube are open.

In a second type they are situated at the ends of tracheal strands and consist of groups of richly protoplasmic cells belonging to the epidermis (as in the leaves of many ferns), or to the subjacent tissue (the commonest type in flowering plants); in this last case the cells in question are known as epithem.