Welwitschiaceae

• Welwitschia mirabilis
• Welwitschia mirabilis

• Query IPNI
• Common Name: Tree Tumbo
• Family: Welwitschiaceae Markgraf.

• Country of Origin: Namib Desert
• Habitat:

• Description: [syn. Welwitschia bainesii]

  A single species of dioecious perennial with short stem and taproot native to S. Angola and SW African deserts, extending into mopane woodland. It is a long-lived plant, deriving moisture from sea-fog dew. Winged seeds germinate in wet years, the cotyledons photosynthesizing for 1.5 years; foliage leaves decussate with respect to cotyledons, of indefinite growth (up to 13.8 cm per year), wearing away at the tips, the apical meristem being lost. Fertile buds are produced on the 'crown' between the leaf bases.

  Inflorescence dichasial, insect pollinated. Females subtended by cone-scales making up a red cone and consisting of a single nucellus enclosed in an integument and another layer derived from two confluent primordia ('perianth') with 2 'bracts'; megaspore mother-cell grows into a prothallus without archegonia. Male flowers subtended by cone-scalesmaking up a red cone and consisting of 2 lateral 'bracts' and a 'perianth' formed by the union of 2 bract-like organs, 6 microsporangiophores and a sterile unitegmic ovule; male gametophyte merely a tube-nucleus, an abortive sterile cell and a cell giving rise to 2 sperm nuclei. As pollen tubes penetrate prothallus, prothallial tubes grow up to meet them in the nucellus, fusion of females and males allegedly occurring in the tubes; many zygotes but only one matures and is dispersed with 'perianth' as a wing.

  Difficult to cultivate requiring desert conditons and room to accomodate its long taproot. Propagated by seeds.