Gnetidae

Gnetidae is a group of gymnosperms comprising the genera Gnetum, Ephedra, and Welwitschia. Its members are unusual among gymnosperms for traits that resemble those of flowering plants.

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Gnetum: A genus of tropical gymnosperms, mostly woody vines or trees, with broad leaves and seeds enclosed in fleshy coverings. It represents the tropical, broad-leaved branch of Gnetidae.
Strobilus: A cone-like reproductive structure made of closely arranged sporophylls or other reproductive organs. Gnetidae bears reproductive structures whose forms vary across its three genera.
Gnetophyte: A gymnosperm lineage comprising Gnetum, Ephedra, and Welwitschia, commonly treated as a class or clade. Gnetophyte is the broader lineage name often used for the plants grouped as Gnetidae.
Angiosperm: A flowering plant whose seeds develop enclosed within an ovary that matures into a fruit. Gnetophytes share some traits with flowering plants but lack flowers and enclosed ovules.
Ephedra: A genus of gymnosperms comprising mostly shrubs with jointed green stems and scale-like leaves. Its dryland shrubs contrast with the other two genera's growth forms.
Double fertilization: A process in which two sperm cells participate in fertilization events within one ovule. Some gnetophytes show a form of this process, distinct from flowering-plant double fertilization.
Molecular phylogenetics: The study of evolutionary relationships using DNA, RNA, or protein sequence comparisons. Molecular evidence has reshaped hypotheses about gnetophyte relationships to other seed plants.
Anthophyte hypothesis: The hypothesis that gnetophytes are closely related to flowering plants based on shared reproductive traits. It interprets similarities that molecular phylogenies do not support as a close relationship.
Welwitschia: A desert gymnosperm species native to the Namib region, with a short trunk and two continuously growing leaves. This distinctive species is the sole member of its genus.
Xylem vessel: A water-conducting tube formed from vessel elements joined end to end in vascular plants. Vessels occur in most gnetophytes, an uncommon feature among gymnosperms.