Tree tumbo, tumboa.
Male red pollen cones, resembling those of Ephedra, appearing in groups of 2-3 terminally on each branch. Female ovulate cones also arising from branched reproductive shoots, each red cone consisting of a single nucellus enclosed in an integument and another layer derived from two confluent primordia ('perianth') with 2 'bracts'.
Leaves typically grow at a rate of 8-15 cm/yr on mature plants, some Welwitschia mirabilis have been found with leaves measuring 1.8 m wide and 6.2 m long, suggesting potential ages of 500-5000 years.
The surface that this leaf covers helps the plant to survive at a temperature on the soil as high as 65 'C. It keeps the soil under the plant cool and moist. The leafs grow annually an average 13.8 sm. Therefore the plant can produce up to 150 m of leaf tissue over a growth period of 1000 years. The leaves are on average 1.4 mm thick. The leaves that lay on the sand surface also prevent wind erosion. Even under gale force conditions the broad leaves remain rigid and immobile. Absorbtion of water through the stomata must be regarded as very interesting, this characteristics of the leaves has ensured the species survival. The stomata remains open until the fog has lifted and although much of the water that has condensed on the leaves runs off the direct intake of a proportion of this water takes place.
Unlike other plants the stomata are open under foggy conditions and closed when it is hotter. This ensures that no water is evaporated during the heat of the day.
Most plants absorb water from the soil through their roots. This water is then transported to the stem and the leaves, the water is then lost by evaporation through the stomata. The Welwitschia mirabilis works the other way around. It absorbs water from fog through the millions of stomata on the surfaces of it's large leaves. From there the water is transported to the roots, where it is stored.
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