Humulus lupulus
Hops is the closest relative of hemp and was first mentioned by Pliny the Elder. Hops appears in the works of all of the fathers of botany and was botanically described by Linneaus. The use of hops as a beer additive was a practice invented by monks towards the end of the Middle Ages by Christian monks, who had a great interest in the anaphrodisiac qualities of the hops flowers. The monks ingested huge amounts of beer so that they could resist the temptations of the devil.
Hops produces a yellow coloring, one used for dying, and the bitter substances of the hop has antibacterial, antimyotic, spasmolytic and estrogenic effects. Abbé Adalhart was the first to document the use of hops in beer. However, this did not become commonplace until the sixteenth century, when the Bavarian Purity Law - the first German drug law - restricted beer additives.