Welwitschia

From Wikipedia, the free encyclopedia

Welwitschia

Scientific classification

Kingdom:	Plantae
Division:	Gnetophyta
Class:	Gnetopsida
Order:	Welwitschiales
Family:	Welwitschiaceae
Genus:	Welwitschia
Species:	W. mirabilis

Binomial name

Welwitschia mirabilis
Hook.f.

Welwitschia is a monotypic genus of gymnosperm plant, comprised solely of the very distinct Welwitschia mirabilis. It is the only genus of the family Welwitschiaceae, in the order Welwitschiales, in the division Gnetophyta. The plant is considered a living fossil (Lewington and Parker, 118).

Female plant

This is a desert plant which grows from a short, thick trunk, with only two leaves that continuously grow from their base, and a long, thick taproot. After germination, the cotyledons grow to 25-35 mm in length, and are followed shortly afterwards by the appearance of the two permanent leaves. These leaves are produced opposite that of the cotyledons, and continue to grow throughout the life of the plant, eventually growing to 2-4 m long and usually becoming split into several strap-shaped sections. After these appear, two cotyledonary buds appear; in these, the growing tip dies, causing elongation of the buds. Growth continues sideways, which forms the obconical growth of the stem. The species is dioecious, with separate male and female plants.

The age of the plants is difficult to assess, but it is believed that they are very long-lived, possibly living 1000 years or more. Some individuals may be more than 2000 years old.

The largest known Welwitschia, nicknamed "The Big Welwitschia", stands 1.4 m tall and is over 4 m in diameter.

The plant is thought to absorb water through peculiar structures on its leaves, harvesting moisture from the dew that comes into the desert every night. Named after Dr. Friedrich Welwitsch who discovered it in 1860, it is generally considered to be one of the oddest plants in existence. Although considered endangered due to its very slow growth and the fact that older plants are desired by collectors, a fair number of plants exist in the wild. The plants living in Angola are generally considered to be better protected than the plants in Namibia, owing to the relatively high concentration of landmines in Angola, which keep collectors away^{[citation needed]}.

The species grows readily from seed, which may be purchased from specialty seed dealers. The seed must be kept moist for the first couple of weeks and exposed to as much heat and light as possible during this time. Seeds collected from the wild are often heavily contaminated with spores of Aspergillus niger, which causes them to rot shortly after they germinate. Seeds from the Kirstenbosch National Botanical Garden in Cape Town, South Africa, or other cultivated sources are much cleaner and less likely to rot.