Horsetail

[Swede]

Horsetail is a very primitive perennial plant with dark-green hollow, jointed or segmented stems 1/4 to 1/2 inch thick with no true leaves. Stems may be singular or have whorls of branches. Only single stems produce the cone-shaped spore producing body at the tip. Horsetails can be standing in water or in wet areas. Horsetail stems contain silicon crystals (i.e. sand) embedded in its tissue. This gritty texture gives it a common name of "scouring rush".

http://aquaplant.tamu.edu/database/emergent_plants/horsetail.htm