| Viscum | |
|---|---|
 | |
| Viscum album growing on aPopulus species | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Order: | Santalales |
| Family: | Santalaceae |
| Genus: | Viscum L. |
| Type species | |
| Viscum album | |
| Species | |
See text | |
Viscum is a genus of about 70–100 species ofmistletoes, native to temperate and tropical regions ofEurope,Africa,Asia andAustralasia.[1] Traditionally, the genus has been placed in its own familyViscaceae, but recent genetic research by theAngiosperm Phylogeny Group shows this family to be correctly placed within a larger circumscription of thesandalwood family,Santalaceae. Its name is the origin of the English wordviscous, after the Latinviscum, a stickybird lime made from the plants' berries.
They are woody,obligate hemiparasiticshrubs with branches 15–80 centimetres (5.9–31.5 in) long. Their hosts are woody shrubs andtrees. The foliage is dichotomously or verticillately branching, with opposite pairs or whorls of greenleaves which perform somephotosynthesis (minimal in some species, notablyV. nudum), but with the plant drawing its mineral and water needs from the host tree. Different species ofViscum tend to use different host species; most species are able to use several different host species.
Theflowers are inconspicuous, greenish-yellow, 1–3 millimetres (0.039–0.118 in) diameter. Thefruit is aberry, white, yellow, orange, or red when mature, containing one or moreseeds embedded in very sticky juice; the seeds are dispersed whenbirds (notably themistle 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; eating the fruit causes a weak pulse and acute gastrointestinal problems including stomach pain anddiarrhea.[2] At least one of the active ingredients is thelectinviscumin, which is intensely toxic. It inhibits protein synthesis by catalytically inactivatingribosomes.[3] In spite of this, many species of animals are adapted to eating the fruit as a significant part of their diet.[4]
†Viscum morlotii from the earlyMiocene, has been described fromfossil leaf compressions that have been found in the Kristina Mine atHrádek nad Nisou inNorth Bohemia, theCzech Republic.[5]
