Why are Gnetum and Welwitschia described as dioecious plants?

Gnetum and Welwitschia are described as dioecious plants because they possess individuals that produce only one type of reproductive structure—either pollen-producing (staminate) or seed-producing (ovulate) cones—rather than both on the same plant.12

In botany, the term dioecious refers to species where male and female reproductive parts are borne on separate individual plants. While some members of the related genus Ephedra may occasionally bear both types of cones on a single plant, Gnetum and Welwitschia consistently exhibit this separation of sexes. This reproductive strategy is significant because it ensures genetic outcrossing, as pollen must be transferred between distinct male and female individuals to achieve fertilization.12