Bulliform cells check the water loss. Bulliform or motor cells are modified epidermal cells present in monocots or grasses. Under stressed conditions, they help in shutting down stomata and thus reduce water loss through transpiration.

(a) Radial Vascular Bundle The xylem and phloem are present on the separate radii of the root. This arrangement of vascular bundle is known as radial vascular bundle.

(b) Polyarch Xylem When many strands of xylem are present, it is referred to as polyarch condition-a characteristic feature of monocot root.

(c) Well Developed Pith Dicot stem and monocot roots have well developed pith formed of parenchymatous cell with intercellular spaces..

Bulliform cells are bubble shaped cells present in grasses. Loss of turgor pressure in these cells causes leaf to curl during water stress, thus reduce transpiration.

Interfascicular and intrafascicular cambia together form a ring of cambium called cambial ring. It is formed due to the meristematic activity of cambium. The cambium which is found between the xylem and phloem is called fasicular or intrafasicular cambium and the newly formed cambium between the two vascular bundle is known as interfasicular cambium. Both type of cambium combine to form the cambial ring.

Phellogen is a meristematic tissue, while phelloderm is a permanent tissue. Phellogen (cork cambium) develops from the cortical cells, sometimes from pericycle cells. These cells actively divide and forms phellem on outerside and phelloderm (cortex cells)innerside on so phelloderm takes its origin from phellogen.