Collier's New Encyclopedia (1921)/Hop
HOP, in botany, Humulus lupulus, the only known species of the genus Humulus. The root, which is perennial, annually sends forth long, weak, rough, twining stems. The leaves somewhat resemble those of the vine, but are rougher. It has an aromatic odor, sent forth by glands containing a resinous secretion. The hop is indigenous in England, but grows also in the United States, in Belgium, and Bavaria. Bryonia dioica is sometimes called wild hop. The native hop of Australia is (1) Dodonœa, the seed vessels of which are there used in the manufacture of beer; (2) Daviesia lætifolia. Hops are boiled with the wort in brewing beer. They impart a bitter taste and aromatic flavor, and prevent fermentation from being too rapid.
In pharmacy lupulus is the designation of hop. The dried catkins of the female plant of H. lupulus are from the common hops. They are used to prepare infusion of hop, tincture of hop, and extract of hop.