Search results
Results From The WOW.Com Content Network
Unambiguous fossils of cycads are known from the Early-Middle Permian onwards. [26] Cycads were generally uncommon during the Permian. [27] The two living cycad families are thought to have split from each other sometime between the Jurassic [17] and Carboniferous. [28] Cycads are thought to have reached their apex of diversity during 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 .
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 ...
Motile sperm are also produced by many protists and the gametophytes of bryophytes, ferns and some gymnosperms such as cycads and ginkgo. The sperm cells are the only flagellated cells in the life cycle of these plants. In many ferns and lycophytes, cycads and ginkgo they are multi-flagellated (carrying more than one flagellum). [34]
The sperm of members from the genus are large, as is typical of cycads, and Z. roezlii is an example; its sperm are approximately 0.4 mm long and can be seen by the unaided eye. [ 11 ] It was long believed that Zamia plants, like all cycads, relied completely on wind pollination .
In ferns and seed plants (including cycads, conifers, flowering plants, etc.) the sporophyte is the dominant generation; the obvious visible plant, whether a small herb or a large tree, is the sporophyte, and the gametophyte is very small. In bryophytes and ferns, the gametophytes are independent, free-living plants, while in seed plants, each ...
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 ...
Encephalartos lehmannii is a low-growing palm-like cycad in the family Zamiaceae.It is commonly known as the Karoo cycad and is endemic to South Africa. [3] The species name lehmannii commemorates Prof J.G.C. Lehmann, a German botanist who studied the cycads and published a book on them in 1834. [3]