Draw illustrations to bring out anatomical difference between

$(a)$ Monocot root and dicot root

$(b)$ Monocot stem and dicot stem

What part of the plant would show the following :

$(a)$ Radial vascular bundle

$(b)$ Polyarch xylem

$(c)$ Well developed pith

In old trees the greater part of secondary xylem is dark brown and resistant to insect attack due to:

$(a)$ secretion of secondary metabolities and their deposition in the lumen of vessels.

$(b)$ deposition of organic compounds like tannins and resins in the central layers of stem.

$(c)$ deposition of suberin and aromatic substances in the outer layer of stem.

$(d)$ deposition of tannins, gum, resin and aromatic substances in the peripheral layers of stem.

$(e)$ presence of parenchyma cells, functionally active xylem elements and essential oils.

Choose the correct answer from the options given below:

Vascular bundles in monocotyledons are considered closed because

Assertion : In collateral vascular bundles, phloem is situated towards inner side.
Reason : In monocot stem, cambium is present