| Lignins occur in great quantity in the secondary cell walls of fibres, xylem vessels and tracheids. |
| Vessel elements, tracheids, fibres, sieve tube elements, sieve cells, and parenchyma cells are the major components of vascular tissue. |
| Archaeosigillaria had an exarch actinostele with scalariform and reticulate tracheids. |
| It can be seen in Fig 3b that the tracheids are pulling apart along their centre lines. |
| In the rays, they operate as transverse tracheids transporting water and mineral nutrients in a radial direction. |
| In conifers, the tracheids, which account for most of the wood, give the tree rigidity and form most of the xylem. |
