TRACHEAE (XYLEM VESSELS)

Tracheae are dead Tracheid cells arranged one above the other in a linear manner and which lose their partition wall and form a continuous tubular, structure for conduction. Tracheae show various types of thickenings in their walls. Tracheae have a better conducting capacity because of their larger lumen. The Tracheae provide mechanical strength and rigidity due to thickenings of lignin. The Tracheae are found in certain pteridophytes, certain higher gymnosperms and in the angiosperms. Tracheae is lacking in certain higher gymnosperms, saprophytic and parasitic plants and fleshy plants.