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The gymnosperms (/ ˈ dʒ ɪ m n ə ˌ s p ɜːr m z,-n oʊ-/ ⓘ JIM-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 ...
A far more rudimentary form of double fertilization occurs in the sexual reproduction of an order of gymnosperms commonly known as Gnetales. [3] Specifically, this event has been documented in both Ephedra and Gnetum, a subset of gnetophytes. [7] In Ephedra nevadensis, a single binucleate sperm cell is deposited into the egg cell. Following the ...
Cordaites is a genus of extinct gymnosperms, related to or actually representing the earliest conifers. These trees grew up to 100 feet (30 m) tall and stood in dry areas as well as wetlands. Brackish water mussels and crustacea are found frequently between the roots of these trees.
This fixed the position of Gymnosperms as a class distinct from Dicotyledons, and the term Angiosperm then, gradually, came to be accepted as the suitable designation for the whole of the flowering plants (other than Gymnosperms), including the classes of Dicotyledons and Monocotyledons. [4] This is the sense in which the term is used, today. [5]
Gymnosperms are divided into 12 families of trees, shrubs and woody vines. [5] Sequoiadendron giganteum, the giant redwood, is the largest tree in the world, and Sequoia sempervirens, the coastal redwood, is the tallest. [6] Ginkgo trees tolerate urban pollutants well, and are often planted in and near cities. [7]
Gnetum is a genus of gymnosperms, the sole genus in the family Gnetaceae within the Gnetophyta.They are tropical evergreen trees, shrubs and lianas.Unlike other gymnosperms, they possess vessel elements in the xylem.
The wood of gymnosperms such as pines and other conifers is mainly composed of tracheids. [2] Tracheids are also the main conductive cells in the primary xylem of ferns. [3] The tracheid was first named by the German botanist Carl Gustav Sanio in 1863, from the German Tracheide. [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.