Viscum

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Viscum

Description

Aerial stem-parasitic shrubs, glabrous, monoecious or (not in Malesia) dioecious. Leaves opposite, normally developed or rudimentary; normally developed leaves entire, unifacial, curvinerved, usually with 3 or 5 veins visible; rudimentary leaves bract-like, c. 1 mm long. Inflorescences terminal or axillary, basically a 3-flowered cymule, sometimes reduced to 1 flower or enlarged by development of adventitious flowers; bracts small, triangular, in pairs forming a boat-shaped cupule subtending each cymule. Fruit narrow-ellipsoid to globose, smooth or tuberculate; tepals usually caducous, rarely persistent as a crown on the fruit.

Distribution

Africa: present Asia-Tropical: Europe: present eastwards to eastern Asia, Malesia and Australia: present
Genus of c. 100 species distributed in Europe, throughout Africa, and eastwards to eastern Asia, Malesia and Australia. In Malesia 9 species, of which probably 4 are endemic, without a distinct centre of species richness.

Morphology

In most species of Viscum the stems long remain green. The basic inflorescence unit is a small 3-flowered dichasium (cymule), in Malesia usually with both male and female flowers, although all-female cymules are sometimes produced when flowering is prolific. In some monoecious species the male flowers are central in the cymule; in others they are lateral. Cymules often develop successively at each node.

Taxonomy

For a revision of Asian and Malesian species, see .

Citation

L., Gen. PI., ed. 5. 1754: 448