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In extinct groups, further protection was afforded to the spores by the presence of whorls of bracts - big pointed microphylls protruding from the cone. The extant horsetails are homosporous, but extinct heterosporous species such as Calamostachys casheana appear in the fossil record. [6] The sporangia open by lateral dehiscence to release the ...
Equisetum (/ ˌ ɛ k w ɪ ˈ s iː t əm /; horsetail) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. [2]Equisetum is a "living fossil", the only living genus of the entire subclass Equisetidae, which for over 100 million years was much more diverse and dominated the understorey of late Paleozoic forests.
Microphylls contain a single vascular trace. The clubmosses and horsetails have microphylls, as in all extant species there is only a single vascular trace in each leaf. [ 2 ] These leaves are narrow because the width of the blade is limited by the distance water can efficiently diffuse cell-to-cell from the central vascular strand to the ...
Equisetum arvense, the field horsetail or common horsetail, is an herbaceous perennial plant in the Equisetidae (horsetails) sub-class, native throughout the arctic and temperate regions of the Northern Hemisphere. It has separate sterile non-reproductive and fertile spore-bearing stems growing from a perennial underground rhizomatous stem system.
Equisetum fluviatile, the water horsetail or swamp horsetail, is a vascular plant in the horsetail family Equisetaceae. It is a perennial herbaceous pteridophyte that reproduces using spores . Description
Equisetum hyemale (rough horsetail [2]) is an evergreen perennial herbaceous pteridophyte in the horsetail family Equisetaceae native to Eurasia and Greenland. It was formerly widely treated in a broader sense including a subspecies (subsp. affine ) in North America, but this is now treated as a separate species, Equisetum praealtum .
Equisetum palustre, the marsh horsetail, [2] is a perennial herbaceous pteridophyte belonging to the subclass of horsetails (Equisetidae). It is widespread in cooler regions of Eurasia and North America .
The stems are the stoutest of any horsetail, 1–2 cm diameter (up to 3.5 cm (1.33 inches) in diameter in some populations), [5] and bear numerous whorls of very slender branches; these branches are not further branched, but some terminate in spore cones. Unlike some other horsetails, it does not have separate photosynthetic sterile and non ...