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
What It Is to Burn with boiling liquid. Doherty said they "just wanted some cool imagery". The art direction and design were done by P.R. Brown, who also did the photography with Kris McCaddon. Initial pressings of the album contained a demo version of "What It Is to Burn", produced by Chris Fuderich. It was replaced on later pressings with a re-recorded version, produced by Trombino. These later pressings were available from June onwards. The UK edition, released on June 2, included an acoustic version of "Letters to You" and the demo of "What It Is to Burn" as bonus tracks. Following the album's release,