The Gnetales (Ephedra, Gnetum and Welwitschia) represent a fascinating group of nonflowering seed plants (gymnosperms). This group of plants has intrigued plant biologists for well over a century due, in part, to their interesting growth habits, medicinal properties, unusual reproductive features, and status a potential link between flowering and other nonflowering seed plants. Indeed, the reproductive biology of Gnetales has increased our understanding of the origin of angiosperms including the process of double fertilisation. The phylogenetic position of Gnetales has been highly debated over the years. Early studies, based largely on structural data, concluded that the Gnetales are monopyletic and represent the sister group to angiosperms (‘anthophyte’ hypothesis). More recent studies provide evidence that the Gnetales represent the sister group to conifers (‘Gnetifer’ hypothesis) or are embedded within conifers and represent the sister group to Pinaceae (‘Gnepine’ hypothesis). Regardless of their phylogenetic position, various structural features of Gnetales have a strong bearing on our understanding of evolutionary trends in seed plants.

Key Concepts:

• Members of the Gnetales are gymnosperms that possess some angiosperm‐like features.
  
• A modified form of double fertilisation occurs in Gnetales.
  
• Ephedra is a shrub that produces ephedrine, a stimulant and decongestant found in certain weight‐loss and energy‐boosting products.
  
• Welwitschia is endemic to the Namib desert in Africa and is considered by many to be one of the most bizarre plants on Earth.