Search results
Results From The WOW.Com Content Network
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 ...
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 ]
Horsetails (species of Equisetum) have spores which are all of the same size. [28] Spores of two distinct sizes (heterospory or anisospory): larger megaspores and smaller microspores. When the two kinds of spore are produced in different kinds of sporangia, these are called megasporangia and microsporangia. A megaspore often (but not always ...
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 ...
Most algae have dominant gametophyte generations, but in some species the gametophytes and sporophytes are morphologically similar . An independent sporophyte is the dominant form in all clubmosses , horsetails , ferns , gymnosperms, and angiosperms that have survived to the present day.
The extant spermatophytes form five divisions, the first four of which are classified as gymnosperms, plants that have unenclosed, "naked seeds": [1]: 172 Cycadophyta, the cycads, a subtropical and tropical group of plants, Ginkgophyta, which includes a single living species of tree in the genus Ginkgo,
Named Gondwanax paraisensis, the four-legged reptile species was roughly the size of a small dog with a long tail, or about 1 meter (39 inches) long and weighing between 3 and 6 kg (7 to 13 pounds ...
In some Gnetophyta species, the germ cell will release two sperm nuclei that undergo a rare gymnosperm double fertilization process occurring solely with sperm nuclei and not with the fusion of developed cells. [10] [13] After fertilization is complete in all orders, the remaining male gametophyte tissue will deteriorate. [11]