Epidermis- It consists of a single layer of cells at the outermost region of the stem. The outer surface is covered by a thick cuticle.Epidermis contains stomata here and there.
Hypodermis:
It is present just below the epidermis and consists of two to three layers of sclerenchymatous cells.
Ground tissues:
ADVERTISEMENTS:
It extends from below the hypodermis to the centre of the stem. It consists of many layers of thin-walled parenchymatous cells with intercellular spaces. It is not differentiated into cortex, endodermis and pericycle.
Vascular bundle:
Vascular bundles numerous and are of different sizes. These are scattered in the ground tissue. The vascular bundles present towards the periphery are smaller and numerous. On the other hand, the vascular bundles lying at the center are bigger and fewer. Each vascular bundle is oval and is surrounded by sclerenchymatous bundle sheath. It is conjoint, collateral and closed. Xylem consists of vessels tracheids and wood parenchyma. Two bigger vessels called metaxylem are present laterally and two smaller vessels called protoxylem are present in radial row towards the center.
Vessels are arranged in ‘Y’ shaped manner. The lower protoxylem is opened to a water-containing cavity. Phloem is present above the xylem and is composed of sieve tubes and companion cells only. Phloem parenchyma is absent. The outer phloem is called protophloem, which is disorganized and is present in the form of broken mass of cells. The inner phloem is called metaphloem, which is composed of sieve tube and companion cells.