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Cycads / ˈ s aɪ k æ d z / are seed plants that typically have a stout and woody trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male or female. Cycads vary in size from having trunks only a few centimeters to several meters tall.
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 .
Spermatophytes: Division: † Pteridospermatophyta: Groups included †Calamopityales †Callistophytales †Caytoniales †Gigantopteridales †Glossopteridales †Lyginopteridales †Medullosales †Peltaspermales †Corystospermales (also referred to as Umkomasiales) †Petriellales; Excluded Angiospermae (flowering plants) Cycadales (cycads ...
In the spermatophytes, the seed plants, the sporophyte is the dominant multicellular phase; the gametophytes are strongly reduced in size and very different in morphology. The entire gametophyte generation, with the sole exception of pollen grains (microgametophytes), is contained within the sporophyte.
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 ...
This contrasts with the haplocheilic stomata of cycads and conifers. In haplocheilic stomata, the ring of subsidiary cells are not derived from the same original structures as the guard cells. This fundamental difference is the main way to differentiate bennettitalean and cycad foliage. [5] Zamites persica
The Natal cycad is dioecious, having male and female cones on separate plants. The male cones are velvety and about 45 by 11 cm (18 by 4 in) in size. Pollen is produced from April to June. The two or three female cones are slightly woolly, yellowish-green and cylindrical, 55 by 25 cm (22 by 10 in) in size, the scales being covered with small knobs.
All that can be said at present is that they were spermatophytes. It is also highly unlikely that they were close relatives of acrogymnosperms, cycads or ginkgos, because these lineages were already established and distinct in the Late Permian. [5] Vegetative leaves of Emplectopteris were at one time included in this group.