differences of gnetophytes and angiosperms.enumerate

The gnetophyta, named for the genus Gnetum (Ephedra and
Welwitschia are the other two extant genera), is an ancient group that has
characteristics of both angiosperms and gymnosperms. This division of land plants first
appears in the fossil record during the Triassic, and was widespread during the
Carboniferous.

Gnetophyta are similar to angiosperms
because both groups have vessel elements in the xylem, a feature lacking in conifers and
cycads. Like the angiosperms, Welwitschia and Gnetum also demonsrate double
fertilization; however in angiosperms, this results in an embryo and its associated
endosperm material arising from two separate sperm, whereas in gnetophytes the one
embryo develops into the seed and the other is aborted. Additionally,the gnetophyte egg
migrates toward the pollen tube, an unusual event only seen in this
group.

The reproductive structures of the gnetophytes are
generally considered to be flower-like. This group also demonstrates netted venation
similar to that found in angiosperms.