The Collaborative International Dictionary of English v.0.48:

Ixtle \Ix"tle\, Ixtli \Ix"tli\([i^]x"tl[-e]), n.
   1. (Bot.) A Mexican name for a variety of Agave rigida,
      which furnishes a strong coarse fiber; also, the fiber
      itself, which is called also pita, and Tampico fiber.
      [Written also istle.]
      [1913 Webster] Ixtle

The Collaborative International Dictionary of English v.0.48:

Tampico fiber \Tam*pi"co fi"ber\ or Tampico fibre \Tam*pi"co
fi"bre\
   A tough vegetable fiber used as a substitute for bristles in
   making brushes. The piassava and the ixtle are both used
   under this name.
   [1913 Webster]