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
Viscum nudum"), but with the plant drawing its mineral and water needs from the host tree. Different species of "Viscum" tend to use different host species; most species are able to use several different host species. The flowers are inconspicuous, greenish-yellow, diameter. The fruit is a berry, white, yellow, orange, or red when mature, containing one or more seeds embedded in very sticky juice; the seeds are dispersed when birds (notably the mistle thrush) eat the fruit, and remove the sticky seeds from the bill by wiping them on tree branches where they can germinate. "Viscum" species are poisonous to humans;