Water hemlock plant. Historical artwork of the water hemlock or cowbane plant (Cicuta virosa). This poisonous semi-aquatic plant produces tetanic convulsions when ingested and is fatal to cattle and humans. The roots (lower right) are especially toxic. Leaves (upper right) and flowers (upper left) are also shown. From The Instructive Picture Book or Lessons from the Vegetable World, Charlotte Mary Yonge, 1857.