Opuntia pailana up to 9 centimeters width. The areoles with dark color support grey-yellow glochids, with long white hairs of trichome. The areols support also thorns 2 to 3 centimeters long with white or light grey color, with some darker strips. Most often, they are three, or six to eight on older plants. Opuntia pailana Opuntia pailana is a species of the genus "Opuntia" in the family Cactaceae. The name "pailana" comes from the sierra de la Paila in the state of Coahuila Mexico where it was discovered. The first description was published by Wilhelm Weingart in 1929 in the book "Monatsschrift
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