Pteridophyta - Characteristics, Life Cycle, Classification.
Gnetophyta is a division of plants, grouped within the gymnosperms (which also includes conifers, cycads, and ginkgos), that consists of some 70 species across the three relict genera: Gnetum (family Gnetaceae), Welwitschia (family Welwitschiaceae), and Ephedra (family Ephedraceae).The class Gnetopsida is characterized by flowering gymnosperms. All of the plants in this class posses some type of flower or cone. This characteristic leads to the inference that plants in this class are the link between conifers and angiosperms.Distinguishing characteristics of the phylum Gnetophyta include the presence of both tracheids and vessels in their xylem tissue, a unique fertilization feature in which a tube grows from the eggs to unite with pollen tubes, and being the only division of gymnosperms that undergo double fertilization.
Essay on the Embryogeny in Gymnosperms: The process leading to the formation and development of embryo is called embryogeny. In majority of the living gymnosperms, except some members (e.g. Sequoia sempervirens, Welwitschia and Gnetum) the initial changes in the development of embryo include the free-nuclear divisions.Alternative Title: Ginkgophyta Ginkgophyte, any member of the division Ginkgophyta, a group of gymnospermous plants of particular interest to paleobotanists. Two of the three genera of ginkgophytes, Ginkgoites and Baiera, are extinct. The third genus, Ginkgo, has only one member, Ginkgo biloba, commonly called the ginkgo tree.
Global Biodiversity Information Facility. Free and Open Access to Biodiversity Data.
