Genus Equisetum L.
Fam: Equisetaceae
Genus: Equisetum L.
English Name: HorsetailDescription:
Equisetum (/ˌɛkwɪˈsiːtəm/; horsetail, snake grass, puzzlegrass) 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. Some equisetids were large trees reaching to 30 m (98 ft) tall.[3] The genus Calamites of the family Calamitaceae, for example, is abundant in coal deposits from the Carboniferous period. The pattern of spacing of nodes in horsetails, wherein those toward the apex of the shoot are increasingly close together, inspired John Napier to invent logarithms.[4]
A superficially similar but entirely unrelated flowering plant genus, mare's tail (Hippuris), is occasionally referred to as "horsetail", and adding to confusion, the name "mare's tail" is sometimes applied to Equisetum.[5]
Despite centuries of use in traditional medicine, there is no evidence that Equisetum has any medicinal properties.
Description
Equisetum leaves are greatly reduced and usually non-photosynthetic. They contain a single, non-branching vascular trace, which is the defining feature of microphylls. However, it has recently been recognised that horsetail microphylls are probably not ancestral as in lycophytes (clubmosses and relatives), but rather derived adaptations, evolved by reduction of megaphylls.[7]
The leaves of horsetails are arranged in whorls fused into nodal sheaths. The stems are usually green and photosynthetic, and are distinctive in being hollow, jointed and ridged (with sometimes 3 but usually 6–40 ridges). There may or may not be whorls of branches at the nodes.
Spores
The spores are borne under sporangiophores in strobili, cone-like structures at the tips of some of the stems. In many species the cone-bearing shoots are unbranched, and in some (e.g. E. arvense, field horsetail) they are non-photosynthetic, produced early in spring. In some other species (e.g. E. palustre, marsh horsetail) they are very similar to sterile shoots, photosynthetic and with whorls of branches.
Horsetails are mostly homosporous, though in the field horsetail, smaller spores give rise to male prothalli. The spores have four elaters that act as moisture-sensitive springs, assisting spore dispersal through crawling and hopping motions after the sporangia have split open longitudinally.[8]
From Wikipedia, the free encyclopedia
Distribution in Bulgaria: (Conspectus of the Bulgarian Vascular Flora) = conspectus&gs_l= Zlc.
Distribution:
Genera
1. The vagina with 3 to 5 large teeth. Spore-bearing stems are chlorophyll-free and simple, later turn green and branch. The branches
branched drooping, gathered in many vertebrae ................................................................................................. ( 5) E. sylvaticum
1*. Vaginas with six or more tiny teeth; plants with other characteristics ......................................................................................... 2.
2. The stems are chlorophyll-free and simple. Infertile chlorophyll-bearing and branched .............................................................. 3.
2*. Spore-bearing stems green, resembling barren ......................................................................................................................... 4
3 Vaginas with 6 to 12 lanceolate teeth ............................................................................................................. (1) E. arvense L.
3*. Vaginas with 20 to 30 awl teeth .............................................................................................................. (2) E. telmateia Ehrh.
4 Spore-bearing class at the tip obtuse; stem smooth or almost .smooth ...................................................................................... 5.
4*. The spor bearing class with a sharp tip; the stem is usually rough .............................................................................................. 6.
5 Vagina funnel-shaped, non-adjacent, with up to 10 teeth, with white membranous edge .................................... (4) E. palustre L.
5*. Vagina almost cylindrical with 15 - 30 teeth, almost without white edge, black .............................………….... (3) E. limosum L.
6 Vaginas, extended upwards, back conical, ending in teeth, extended in a filamentous, white, membranous, deciduous tip; stem
strongly branched. ............................................................................................................................ ... (6) E. ramosissimum Desf.
6*. Upper vagina adjacent to the stem, cylindrical, with very short, blunt and black teeth; stem unbranched ……… (7) E. hiemale L.From: „Флора на България”, Н. Стоянов, Б. Стефанов, Б. Китанов, том I, Изд. „Наука и Изкуство”, София, (1966)
References: Wikipedia, the free encyclopedia, „Флора на България”, Н. Стоянов, Б. Стефанов, Б. Китанов, том I, Изд. „Наука и Изкуство”, София, (1966)
SPECIES:
Equisetum arvense L. - Field horsetail, Common horsetail
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