Welwitschiaceae consists of only one species, Welwitschia mirabilis, which may be one of the strangest plants on the planet. It grows only in the Namib Desert of Angola and Namibia and produces just two huge leaves from a short, woody, unbranched stem. The leaves grow an average of 8 to 15 centimeters (3 to 6 inches) per year, and often are split and twisted at their ends, forming a tangled mass. Some Welwitschia leaves have been measured at up to 6 meters (19.7 feet) long. The plants survive in the desert by developing a huge taproot that may extend down nearly 2 meters (6.6 feet). A few plants have been estimated to be close to 2,000 years old. The cones of this odd plant develop from buds on the woody crown between the two leaves. Both the pollen cones and seed cones are compound and consist of two rows of opposite bracts. In the base of these bracts the fertile shoot emerges. Pollen cones bear 6 pollen organs that have fused bases. These are enclosed by 2 sets of bractlike structures. There is an aborted ovule in the middle of the apex. The seed cones are similar in design to the pollen cone; the outer bracts are not fused and inner bracts are long and fused and form an envelope over the ovule.