THE MISTLETOE FAMILY (Santalaceae(Loranthaceae)

Mistletoe is the common name for obligate hemi-parasitic plants in several families in the order Santalales. These plants attach to and penetrate the branches of a tree or shrub by a structure called the haustorium, through which they absorb water and nutrients from the host plant. The name mistletoe was originally applied to Viscum album (European mistletoe, of the family Santalaceae), the only species native in Great Britain and much of Europe. Viscum album can parasitise more than 200 tree and shrub species. All mistletoes are hemi-parasites, bearing evergreen leaves that do some photosynthesis, using the host mainly for water and mineral nutrients, reducing their growth and even killing them in cases of heavy infestation. It is a poisonous plant that causes acute gastrointestinal problems including stomach pain and diarrhea along with low pulse.

European mistletoe is readily recognized by its smooth-edged, oval, evergreen leaves borne in pairs along the woody stem, and waxy white berries, each containing a single seed and carried in dense clusters of two to six. Mistletoe seed germinates on the branch of a host tree or shrub and in its early stages of development is independent of its host. Later it forms a haustorium that penetrates the host tissue and takes water and nutrients from the host plant. The flowers are inconspicuous and single sex, berries only therefore developing on the female plants.

Most mistletoe seeds are spread by birds that eat the fruits (drupes). There are various species of such birds, such as the Mistle Thrush in Europe. Depending on the species of bird, the seeds are regurgitated from the crop, excreted in their droppings, or stick to the bill, from which the bird wipes it onto a suitable branch. The seeds are coated with a sticky material called viscin. The viscin survives such treatment and any bare seed that touches a stem sticks tenaciously. The viscin soon hardens and attaches the seed firmly to its future host, where it germinates and its haustorium penetrates the sound bark

Mistletoe was often considered a pest that kills trees and devalues natural habitats, but was recently recognized as an ecological keystone species, an organism that has a disproportionately pervasive influence over its community. A broad array of animals depend on mistletoe for food, consuming the leaves and young shoots, transferring pollen between plants, and dispersing the sticky seeds. Such interactions lead to dramatic influences on diversity, as areas with greater mistletoe densities support higher diversities of animals. Thus, rather than being a pest, mistletoe has a positive effect on biodiversity, providing high quality food and habitat for a broad range of animals in forests and woodlands worldwide.

(source: Wikipedia)