What is the white sap from rubber trees called?

The white sap from rubber trees is called latex. It is a milky fluid stored in specialized vessels in the bark of trees such as the Pará rubber tree, Hevea brasiliensis.

To collect it, workers make a careful diagonal incision in the bark without cutting deeply into the tree’s growth tissues. The latex flows down the cut and through a small spout into a cup. This process is known as rubber tapping, and the liquid is later processed into natural rubber.

Latex is not the same thing as ordinary plant sap. Sap mainly transports water, minerals, and sugars through a plant, whereas latex is an emulsion containing tiny particles and many dissolved compounds. In the rubber tree, it is produced in laticiferous vessels and may also help defend the plant against herbivores.

The rubber tree originated in the Amazon Basin, but commercial plantations now grow across tropical regions. Indigenous peoples of the Americas used natural latex long before modern industry; the material was used for waterproofing and for balls in the Mesoamerican ballgame. Vulcanization later made rubber far more durable.