In flowering plants,the main water transporting elements are

From both phylogenetic and ontogenetic points of view,which tissue is regarded as the most primitive?

The end walls of tracheids and vessels,respectively,are:

Lignification is associated with

Complex tissues are

$I.$ These tissues are found as layers or patches.
$II.$ It consists of cells which are thickened at the corners.
$III.$ It often contains chloroplasts.
$IV.$ Intercellular spaces are absent.
$V.$ They provide mechanical support to growing parts of plants.
The above characters are attributed to: