Family: Santalaceae |
See citations Plants parasitic on branches of woody angiosperms and gymnosperms, usually shrubby, sometimes herbaceous, usually dioecious, sometimes monoecious. Stems single or multiple; branching usually pseudodichotomous, sometimes percurrent, usually dense and intricate, internodes rounded to compressed, sometimes ribbed and twisted 90° to form a decussate leaf and branching pattern. Leaves usually well developed, sometimes scalelike. Inflorescences axillary and/or terminal, subtended by a pair of fused bracts (bracteal cup), sessile or pedunculate, dichasial cymes, solitary or clustered; monoecious plants usually with dichasia having a central staminate flower and pistillate lateral flowers; staminate unisexual plants usually with (2-)3 flowers per dichasium, pistillate unisexual plants usually with a single flower per bracteal cup. Staminate flowers: tepals 3-4-merous, tepals triangular; anthers multilocular, dehiscing by numerous pores; nectary absent; monoecious plants usually with central flower staminate, lateral flowers pistillate or all flowers in a dichasium of the same sex. Pistillate flowers: 3-4-merous, tepals triangular, distinct; ovaries 0-locular, inferior; styles absent or present and shortly conic; stigmas usually poorly differentiated, sometimes capitate. Fruits berries, pediciellate or sessile, white, yellow, orange or red, uniformly colored, usually smooth, sometimes warty, scars of petal remnants present at top. Seeds mucilaginous when removed from fruit, endosperm slightly flattened, ovate to elliptic in broadest outline; embryo oriented transversely. x = 14. Viscum has about 130 species. It is native to Eurasia Africa, Indian Ocean Islands, and Australia. It is most diverse in tropical and southern Africa, where various species form a decreasing aneuploid series (from × = 14) (D. Wiens 1975). Higher gametic chromosome numbers are the result of polyploidy. Several species of dioecious Viscum show translocation heterozygosity that determines plant sexuality and sex ratios in populations (A. Aparicio 1993; Wiens and B. A. Barlow 1979). References Nickrent, D.L. Viscum in Flora of North America north of Mexico. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=134632. Polhill, R. M. & M. Thulin (1999) M. Viscum, Pp. 143-145 in M. Thulin (Ed.) Flora of Somalia vol. 2. |