Cyperaceae

The family Cyperaceae, or the sedges, is a taxon of flowering plants. They look like grasses or rushes, but are not. They are monocot plants (as are grasses), but belong to a different family. 
The family is large, with some 5,500 species described in about 109 genera. The largest is the "Carex" genus of "true sedges", with over 2,000 species.
Sedges include many wild marsh and grassland plants, and some cultivated ones such as water chestnut ("Eleocharis dulcis") and papyrus sedge ("Cyperus papyrus"). These species are widely distributed, with many in tropical Asia and tropical South America. Sedges may be found growing in almost all environments. Many are wetlands, or have poor soils. Ecological communities dominated by sedges are known as sedgelands.
Features distinguishing members of the sedge family from grasses or rushes are stems with triangular cross-sections (with occasional exceptions) and leaves that are spirally arranged in three ranks (grasses have alternate leaves forming two ranks).