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HORSETAIL (Equisetum)

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Originally appearing in Volume V13, Page 739 of the 1911 Encyclopedia Britannica.
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HORSETAIL (Equisetum) , the See also:sole genus of the botanical natural See also:order Equisetaceae, consisting of a See also:group of vascular cryptogamous See also:plants (see See also:PTERIDOPHYTA) remarkable for the vegetative structure which resembles in See also:general See also:appearance the genera of flowering plants See also:Casuarina and Ephedra. They are herbaceous plants growing from an underground much- 4fejftt4ap jt. From Strasburger's Lehrbtah der Botanik, by permission of Gustav See also:Fischer. Equisetum arvense. A, Fertile shoot, springing B, C, Sporophyllsbearing sporangia, from the rhizome, which which in C have opened. also bears tubers; the D, Spore showing the two See also:spiral vegetative shoots have bands of the perinium. not yet unfolded. F, Dry spores showing the ex- F, Sterile vegetative shoot. panded spiral bands. (A, F, reduced. B, C, D, E, enlarged.) branched rootstock from which See also:spring slender aerial shoots which are See also:green, ribbed, and See also:bear at each See also:node a whorl of leaves reduced to a toothed sheath. From the nodes spring whorls of similar but more slender branches. Some shoots are sterile while others are fertile, bearing at the See also:apex the so-called fructification—a dense See also:oval, oblong conical or cylindrical spike, consisting of a number of shortly-stalked peltate scales, each of which has attached to its under See also:surface a circle of spore-cases (sporangia) which open by a See also:longitudinal slit on their inner See also:side.

The spores differ from those of ferns in their See also:

outer coat (exospore) being split up into four See also:club-shaped hygroscopic threads (elaters) which are curled when moist, but become straightened when dry. In most See also:species the fertile and sterile shoots are alike, both being green and See also:leaf-bearing, but in a few species the fertile are more or less different, e.g. in E. arvense the fertile shoots appear first, in the spring, and are unbranched and not green. Any portion of the underground rhizome when broken off is capable of producing a new plant; hence the difficulty of eradicating them when once established. There are 24 known species of the genus which is universally distributed. The See also:corn horsetail E. arvense, one of the commonest species, is a troublesome See also:weed in clayey cornfields (see fig.). The fructification appears in See also:March and See also:April, terminating in See also:short unbranched stems. It is said to produce See also:diarrhoea in such See also:cattle as eat it. The See also:bog horsetail, E. palustre, is said to possess similar properties. It grows in marshes, ditches, pools and drains in meadows, and sometimes obstructs the flow of See also:water with its dense matted roots. The fructification in this species is cylindrical, and in that of E. limosum, which grows in similar situations, it is ovate in outline. The largest See also:British species, E. maximum, grows in wet sandy declivities by railway embankments or streams, &c., and is remarkable for its beauty, due to the abundance of its elegant branches and the alternately green and See also:white appearance of the See also:stem. In this species the fructification is conical or lanceolate, and is found in April on short, stout, unbranched stems which have large loose sheaths.

Horses appear to be fond of this species, and in See also:

Sweden it is stored for use as See also:winter See also:fodder. E. hyemale, commonly known as the Dutch See also:rush, is much more abundant in See also:Holland than in See also:Britain; it is used for polishing purposes. E. variegatum grows on wet sandy ground, and serves by means of its fibrous roots to bind the See also:sand together. The horsetails are remarkable for the large quantity of See also:silica they contain in the cuticle (hence their value in polishing), which often amounts to See also:half the See also:weight of the ash yielded by burning them; the roots contain a quantity of See also:starch.

End of Article: HORSETAIL (Equisetum)

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