One of the most valuable parts of the hemp plant is the fiber, commonly referred to as "bast," meaning that it grows as a stalk from the ground. Other fibers such as sisal, manila hemp and jute are mistakenly referred to as hemp, yet only Cannabis Sativa is considered "true hemp". Among the characteristics of hemp fiber are its superior strength and durability, and its stunning resistance to rot, attributes that made hemp integral to the shipping industry. The strong, woody bast fiber is extracted from the stalk by a process known as decortication. Hemp fiber contains a low amount of lignin, the organic glue that binds plant cells, which allows for environmentally friendly bleaching without the use of chlorine. In composite form, hemp is twice as strong as wood. All products made with hemp fiber are biodegradable.