A perennial climbing vine, also known by the Latin botanical name Humulus lupulus. The female plant yields flowers of soft-leaved pine-like cones (strobile) measuring about an inch in length. Only the female ripened flower is used for flavouring beer. Because hops reproduce through cuttings, the male plants are not cultivated and are even uprooted to prevent them from fertilizing the female plants, as the cones would become weighed-down with seeds. Seedless hops have a much higher bittering power than seeded. There are presently over one hundred varieties of hops cultivated around the world. Some of the best known are Brewer’s Gold, Bullion, Cascade, Centennial, Chinook, Cluster, Comet, Eroica, Fuggles, Galena, Goldings, Hallertau, Nugget, Northern Brewer, Perle, Saaz, Syrian Goldings, Tettnang and Willamettes. Apart from contributing bitterness, hops impart aroma and flavour, and inhibit the growth of bacteria in wort and beer. Hops are added at the beginning (bittering hops), middle (flavouring hops), and end (aroma hops) of the boiling stage, or even later in the brewing process (dry hops). The addition of hops to beer dates from 7000-1000 BC. In 600 BC Pharaonic Egypt, hops were used to flavour beer and they were cultivated in Germany as early as AD 300 and were used extensively in French and German monasteries in medieval times. Prior to the use of hops, beer was flavoured with herbs and spices such as juniper, coriander, cumin, nutmeg, oak leaves, lime blossoms, cloves, rosemary, gentian, gaussia, chamomile, and other herbs or spices. Around the 14th and 15th centuries, hops superseded other herbs and spices in the production of beer.