Page 18 - LN-ANATOMY OF FLOWERING PLANT

2. Hypodermis
It is 2-3 layered having lignified. sclerenchymatous cells present just below the
epidermis.
3. Ground Tissue
It fills the whole interior of the stem containing parenchymatous cells. A number of
vascular bundles are scattered in it.
4. Vascular System
Each vascular bundle in vascular strand is surrounded by a sheath of sclerenchyma
known as bundle sheath cells. The vascular bundles possesses both phloem and
xylem so, these are conjoint type.
The bundles are endarch with the protoxylem and metaxylem are arranged in the
form. The divergent ends are occupied by two pitted vessels and convergent end by
two smaller spiral vessels lying radially in the centre. A water containing cavity called
lysigenous cavity is present in association with the protoxylem.
It is formed by the breakdown of inner protoxylem vessels and parenchyma during
the earlier stages of growth. The cavity is absent or reduced in the smaller vascular
bundles that occur in contact with sclerenchymatous hypodermis.
Features for Identification of Monocotyledonous Stem
Monocotyledonous stem can he easily identified with the following features
(i) Sclerenchymatous hypodermis present.
(ii) Undifferentiated ground tissue.
(iii) Vascular bundles scattered throughout ground tissue.
(iv) Vascular bundles are conjoint, collateral and closed.
(v) Protoxylem cavity present.