Xan'thium Struma'rium, Broad Cocklebur; N. America. Achenes 2.5 Cm. (1') long, flat, oblong, without pappus, enclosed in the involucre, which is densely beset with hooked prickles. X. spino'sum, Spiny or Thorny Clotbur; N. America, S. Europe; leaves with spines at base 2.5 Cm. (1') long; fertile axillary burs (achenes) crowned with 1 inconspicuous beak. X canaden'se, and its var. echina'tum; achenes, with 2 stout beaks, hooked, 2.5 Cm. (1') long, densely prickly, hispid; river banks, waste places; var. echinatum, smaller plant -- possibly unworthy of variety distinction.