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.