Rhizomatous colonial perennials with annual or perennial green stems, the epidermis with silicified cell walls and often with regularly arranged silicified projections, so that the surface is minutely rough to the touch. 2n=216 or nearly so. 15, cosmop. Sterile but vegetatively vigorous and persistent hybrids are often produced between species of the same subgenus. Some of these are: E. ئerrissii Clute = E. hyemale נlaevigatum; E. جitorale K