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Botanists define vascular plants by three primary characteristics: Vascular plants have vascular tissues which distribute resources through the plant. Two kinds of vascular tissue occur in plants: xylem and phloem. Phloem and xylem are closely associated with one another and are typically located immediately adjacent to each other in the plant.
These groups include the Rhyniopsida, Zosterophyllopsida, Trimerophytopsida, the Lepidodendrales and the Progymnospermopsida. Modern studies of the land plants agree that seed plants emerged from pteridophytes more closer to ferns than lycophytes. Therefore, pteridophytes do not form a clade but constitute a paraphyletic grade.
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 ...
Pteridospermae, the so-called "seed ferns", were one of the earliest successful groups of land plants, and forests dominated by seed ferns were prevalent in the late Paleozoic. Glossopteris was the most prominent tree genus in the ancient southern supercontinent of Gondwana during the Permian period.
They are one of the oldest lineages of extant (living) vascular plants; the group contains extinct plants that have been dated from the Silurian (ca. 425 million years ago). [ 2 ] [ 3 ] Lycophytes were some of the dominating plant species of the Carboniferous period, and included the tree-like Lepidodendrales , some of which grew over 40 metres ...
The group may be treated as an unranked clade, [1] a division under the name Euphyllophyta [2] or a subdivision under the name Euphyllophytina. [3] The euphyllophytes are characterized by the possession of true leaves ("megaphylls"), and comprise one of two major lineages of extant vascular plants. [4]
This is the only type of xylem found in the earliest vascular plants, and this type of cell continues to be found in the protoxylem (first-formed xylem) of all living groups of vascular plants. Several groups of plants later developed pitted tracheid cells independently through convergent evolution.
The only exceptions are Isoetes and Phylloglossum, which independently has evolved multiflagellated sperm cells with approximately 20 flagella [5] [6] (sperm flagella in other vascular plants can count at least thousand at most, but the number is generally much lower, and flagella are completely absent in seed plants except for Ginkgo and ...