(i) It occurs in some arborescent monocots (e.g.,
Dracaena, Yucca, Agave) and storage roots (e.g., beet,
sweet potato).
(ii) In arborescent monocot stems, a secondary cambium
grows in hypodermal region.
It later forms conjunctive tissue and patches of
meristematic cells. The meristematic patches grow
into secondary vascular bundles. Anomalous vascular
bundles also occur in cortex (e.g., Nyctanthes) and
pith (e.g., Boerhavia). In storage roots (e.g., beet),
accessory cambial rings appear on the outside of
endodermis. They produce less secondary xylem, but
more secondary phloem.