Natural rubber at least showed promise as rubber sources, include the rubber fig ("Ficus elastica"), Panama rubber tree ("Castilla elastica"), various spurges ("Euphorbia" spp.), lettuce ("Lactuca" species), the related "Scorzonera tau-saghyz", various "Taraxacum" species, including common dandelion ("Taraxacum officinale") and Russian dandelion ("Taraxacum kok-saghyz"), and perhaps most importantly for its hypoallergenic properties, guayule ("Parthenium argentatum"). The term gum rubber is sometimes applied to the tree-obtained version of natural rubber in order to distinguish it from the synthetic version. The first use of rubber was by the indigenous cultures of Mesoamerica. The earliest archeological evidence of the use of natural latex from the
Ficus vasta not cultivated under domestication, and is disappearing due to human pressure, mainly in its use as firewood. Ficus vasta Ficus vasta (; warka) is a fig plant found in Ethiopia and Yemen. "Ficus vasta" is a large tree, with a massive trunk, and spreading branches whose tips form an inverted bowl up to 50m in diameter. It reaches a height of 25m. The trunk is smooth and grey, and is commonly buttressed. The bark is smooth and grey, except on young branches where it is yellow-white-brown, and flaking when dry. The leaves are elliptical, reaching 25 x 20 cm, hairy,