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Published In: Species Plantarum 2: 1061. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 4/9/2015)
Acceptance : Accepted
Project Data     (Last Modified On 8/5/2009)

 

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1. Equisetum L. (horsetail, scouring rush)

(Hauke, 1963, 1979)

Plants perennial, homosporous, with rhizomes. Aerial stems erect or less commonly ascending, branched or unbranched, green except for the fertile stems of some species, hollow and with longitudinal canals in the tissue, jointed at the nodes, with a ring of longitudinal ridges. Leaves whorled, reduced, fused for part of their length to form a collarlike sheath around the stem, the lobes appearing as small, tan to black teeth or scales along the tip of the sheath. Sporangia saclike, in whorls on the underside of highly modified leaves (sporangiophores), these peltate, hexagonal in surface view, and aggregated in dense whorls into conelike strobili occurring at the stem or branch tips. Spores 35–70 mm in diameter, green, globose, each with 4 spirally curled, white filaments (elaters) that uncurl upon drying. Gametophytes green, growing at or near the soil surface, disk- to cushion-shaped, irregularly lobed. Fifteen species, worldwide.

The strobili of Equisetum species are conelike, with dense, hexagonal plates in surface view. At maturity, the internodes between the whorls of sporangiophores elongate, allowing the spores to be shed. The green spores are relatively short-lived and germinate quickly under proper conditions. The four elaters associated with each spore spread when the spores dry and apparently aid in spore dispersal. Vegetative reproduction of the plants is accomplished by water, as portions of rhizomes are washed downstream during floods and later form new roots and aerial stems.

 

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1 Aerial stems dimorphic; vegetative stems green, with regular whorls of branches; fertile stems pink to tan or white and unbranched at the time that spores are shed 1. Equisetum arvense
+ Aerial stems monomorphic, unbranched or sometimes irregularly branched at some nodes (2)
2 (1) Stems somewhat rough to the touch; leaf sheaths with a broad, dark band near the base, usually also with a white band in the middle and a thin, dark band at the tip, the teeth sometimes persistent at maturity; tips of strobili sharp-pointed 2. Equisetum hyemale var. affine
+ Stems smooth; leaf sheaths green except sometimes for a thin dark band at the tip, the teeth usually shed before maturity; tips of strobili rounded, less commonly with a blunt point 3. Equisetum laevigatum
 
 
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