How do Ephedra, Gnetum, and Welwitschia differ in their growth forms?

The three genera of the division Gnetophyta exhibit distinct growth forms adapted to their respective environments:

• Ephedra: Most species are branched shrubs or occasionally small trees, though some are vinelike and clamber over other vegetation. Their stems are finely ridged and jointed, and they possess small, scalelike leaves.123
• Gnetum: This genus primarily consists of lianas (woody vines) that climb high into trees within tropical rainforests. However, some species, such as G. gnemon, grow as trees that can reach heights of up to 20 metres. Unlike Ephedra, Gnetum species typically have large, broad leaves that resemble those of flowering plants.143
• Welwitschia: This genus is represented by a single, highly unusual species, Welwitschia mirabilis, which is native to the extreme deserts of southwestern Africa. It features a massive, short, cone-shaped crown (stem) that remains mostly hidden by its only two permanent, leathery, straplike leaves, which grow continuously from the base throughout the plant's life.1523