Welwitschia

Welwitschia is a very odd genus of plants native to southwestern Africa, and containing only one species:

Welwitschia mirabilis Hook. f.

Welwitschia is the only genus of the family Welwitschiacae, in the order Gnetales, in the class Gnetopsida.

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.

The age of these plants is difficult to assess, but it's believed that they are very long-lived, possible living to one thousand years or longer.

See also:

• website of the Ecology & Evolutionary Biology Conservatory:
  

http://florawww.eeb.uconn.edu/acc_num/199700061.html

• the Gymnosperm database
  

http://www.botanik.uni-bonn.de/conifers/we/welwitschiaceae.htm