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Gnetophyta (/ n ɛ ˈ t ɒ f ɪ t ə, ˈ n ɛ t oʊ f aɪ t ə /) is a division of plants (alternatively considered the subclass Gnetidae or order Gnetales), 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 ...
The gymnosperms (/ ˈ dʒ ɪ m n ə ˌ s p ɜːr m z,-n oʊ-/ ⓘ nə-spurmz, -noh-; lit. ' revealed seeds ') are a group of woody, perennial seed-producing plants, typically lacking the protective outer covering which surrounds the seeds in flowering plants, that include conifers, cycads, Ginkgo, and gnetophytes, forming the clade Gymnospermae [2] The term gymnosperm comes from the ...
The spermatophytes were traditionally divided into angiosperms, or flowering plants, and gymnosperms, which includes the gnetophytes, cycads, [5] ginkgo, and conifers. Older morphological studies believed in a close relationship between the gnetophytes and the angiosperms, [6] in particular based on vessel elements.
Reduced gametophytes, three cells in male, seven cells with eight nuclei in female (except for basal angiosperms) [10] The gametophytes are smaller than those of gymnosperms. [11] The smaller size of the pollen reduces the time between pollination and fertilization, which in gymnosperms is up to a year. [12] Embryo sac is a reduced female ...
Seed producing plants, which include the angiosperms and the gymnosperms, have a heteromorphic alternation of generations with large sporophytes containing much-reduced gametophytes. Angiosperms have distinctive reproductive organs called flowers, with carpels , and the female gametophyte is greatly reduced to a female embryo sac, with as few ...
The distinction was then formalized by Lindley (1830), dividing what he referred to as the subclass Dicotyledons into two tribes, Gymnosperms and Angiosperms. [d] In the gymnosperms (or Gymnospermae) Lindley included two orders, the Cycadeae and the Coniferae. [8] [9] In his final work (1853) he described Gymnogens as a class with four orders; [10]
Seed plants include two clades with living members, the gymnosperms and the angiosperms or flowering plants. In gymnosperms, the ovules or seeds are not further enclosed. In angiosperms, they are enclosed within the carpel. Angiosperms typically also have other, secondary structures, such as petals, which together form a flower.
Detailed morphological and molecular studies have shown that the group is not actually monophyletic, [2] with proposed floral homologies of the gnetophytes and the angiosperms having evolved in parallel. [3] This makes it easier to reconcile molecular clock data that suggests that the angiosperms diverged from the gymnosperms around 320-300 mya ...