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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.
Angiosperms are dealt with in more detail here; these structures are very different in gymnosperms. [7] In angiosperms, the specialised leaves that play a part in reproduction are arranged around the stem in an ordered fashion, from the base to the apex of the flower. The floral parts are arranged at the end of a stem without any internodes.
The gymnosperms consist of five orders of seed plants: Cupressales, Cycadales, Ginkgoales, Gnetales and Pinales. [a] They developed more than 350 million years ago, long before flowering plants, according to the fossil record. The name comes from the Greek for "naked seed"; the egg cells are not protected by ovaries, as in flowering plants. [4]
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.
Archegoniatae was a higher taxonomic term that indicated those embryophytes having a female sexual organ in the form of an archegonium.The term was first introduced by the Russian botanist Ivan Nikolaevich Gorozhankin (1848–1904) in 1876 to indicate a division including bryophytes, pteridophytes and gymnosperms in contrast to the Gynoeciatae (Angiosperms) with a more complex female organ.
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 ...