Stem of a Dracaena. Light micrograph of a cross- section through the stem of a Dracaena (Darcaena terminalis) of the Agavaceae (Monocotyledons). It has secondary thickening in its stem to form a ring of vascular bundles from a circular meristematic layer (usually this group of plants have only scattered vascular bundles). The agavareae family is used as a source of fibres.