Phylum

Gnetophyta

(Vessel-bearing gymnosperms)

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Living Genera:

 Phylum including three extant families and four genera. This lineage dates back only to the early Cretaceous in the fossil record and is widely considered to be the closest extant relative of the flowering plants.

Vegetative Characteristics: Plants are trees, shrubs, lianes, or stumpy turnip-like. Leaves are simple, opposite or whorled, strap-like in Welwitschiaceae, angiosperm-like in Gnetaceae, or scale-like in Ephedraceae. Secondary xylem contains vessels, as in angiosperms, although the homology of the vessels in the two phylum is in question.

Reproductive Characteristics: Plants are usually dioecious with "flowers" unisexual in compound strobili or "inflorescences". Female flowers have one (rarely paired), erect ovule, a nucellus of two or three coats, and micropyle projecting as a long tube. The female gametophyte often lacks organized archegonia. Male cone mostly compound, and associated with bracts. Fertilization occurs through pollen-tubes with two male nuclei. Double fertilization is recorded for some members of the phylum as in angiosperms, although the two are not exactly homologous. Insect pollination is likely due to cone exudations .