Viscum album originally described by Linnaeus. Its species name is the Latin adjective "albus" "white". It and the other members of the genus "Viscum" were originally classified in the mistletoe family Viscaceae, but this family has since been sunk into the larger family Santalaceae. Several subspecies are commonly accepted. They differ in fruit colour, leaf shape and size, and most obviously in the host trees utilised. European mistletoe is potentially fatal, in a concentrated form, and people can become seriously ill from eating the berries. The toxic lectin viscumin has been isolated from "Viscum album". Viscumin is a cytotoxic protein (ribosome inactivating
What Is and What Should Never Be descending riff [of "What Is and What Should Never Be"] is amazing: It's like a bow is being drawn back, and then it releases. The rhythm of the vocals is almost like a rap. It's insane — one of their most psychedelic songs." This was also one of the first songs recorded by the band for which Robert Plant received writing credit. According to rock journalist Stephen Davis, the author of the Led Zeppelin biography "Hammer of the Gods: The Led Zeppelin Saga", the lyrics for this song reflect a romance Plant had with his wife's younger sister. "What Is