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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.
A strobilus (pl.: strobili) is a structure present on many land plant species consisting of sporangia-bearing structures densely aggregated along a stem. Strobili are often called cones , but some botanists restrict the use of the term cone to the woody seed strobili of conifers.
strobilus) at the tips of some stems. These cones comprise spirally arranged sporangiophores , which bear sporangia at their edges, and in extant horsetails cover the spores externally - like sacs hanging from an umbrella, with its handle embedded in the axis of the cone.
The mature strobili of a horsetail (Equisetum arvense). A cross section through a horsetail strobilus, showing spores with elaters. Liverwort elaters
Equisetites is a "wastebin taxon" uniting all sorts of large horsetails from the Mesozoic; it is almost certainly paraphyletic and would probably warrant being subsumed in Equisetum. But while some of the species placed there are likely to be ancestral to the modern horsetails, there have been reports of secondary growth in other Equisetites ...
Equisetales is an order of subclass Equisetidae with only one living family, Equisetaceae, containing the genus Equisetum (horsetails), as well as a variety of extinct groups, including the tree-like Calamitaceae.
It is an evergreen herbaceous perennial plant, with green stems, each stem usually topped by a spore-bearing strobilus.The stems, produced in late spring and dying down a year and a half or two years later, are 18–150 cm (7.1–59.1 in) (occasionally to 220 cm (87 in)) tall and 6–18 mm (0.24–0.71 in) diameter, usually unbranched; they are ridged, with 14–50 ridges, and bear whorls of ...
Equisetum hyemale strobilus, at Darłówko on the Baltic Sea coast of Poland. Equisetum hyemale is native to central and northern Eurasia, including Iceland, Greenland, Kamchatka and Japan, where it forms clonal colonies in mesic (reliably moist) habitats, often in heavy clay or sandy soils in riparian zones of rivers and streams where it can withstand occasional flooding, but also in lime ...